Hello!
As posted before on this tracking bug (probably the wrong place) https://bugs.launchpad.net/ubuntu/+source/linux-5.4/+bug/1864871, I have the same issue with an old Toshiba Satellite L450 laptop.
I ran the live Ubuntu 20.04 image and the sound was recognized and played well.
In Settings I could see the output Internal speakers.
Then I installed from within the live image Ubuntu and still have sound.
Back then the kernel was 5.4.0-28.32-generic 5.4.30.
I've updated Ubuntu last night and surprise. Now I only have Dummy output (no sound).
I've researched and tested a lot of tricks to make it play but with no luck.
Attached is the pulse audio log file as instructed by @Hui Wang (hui.wang) in https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1875252/comments/5.

The pacmd command result is:

Memory blocks currently allocated: 3, size: 67,6 KiB.
Memory blocks allocated during the whole lifetime: 34834, size: 203,7 KiB.
Memory blocks imported from other processes: 0, size: 0 B.
Memory blocks exported to other processes: 0, size: 0 B.
Total sample cache size: 0 B.
Default sample spec: s16le 2ch 44100Hz
Default channel map: front-left,front-right
Default sink name: auto_null
Default source name: auto_null.monitor
Memory blocks of type POOL: 3 allocated/34834 accumulated.
Memory blocks of type POOL_EXTERNAL: 0 allocated/0 accumulated.
Memory blocks of type APPENDED: 0 allocated/0 accumulated.
Memory blocks of type USER: 0 allocated/0 accumulated.
Memory blocks of type FIXED: 0 allocated/0 accumulated.
Memory blocks of type IMPORTED: 0 allocated/0 accumulated.
28 module(s) loaded.
    index: 0
        name: <module-device-restore>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Automatically restore the volume/mute state of devices"
                module.version = "13.99.1"
    index: 1
        name: <module-stream-restore>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Automatically restore the volume/mute/device state of streams"
                module.version = "13.99.1"
    index: 2
        name: <module-card-restore>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Automatically restore profile of cards"
                module.version = "13.99.1"
    index: 3
        name: <module-augment-properties>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Augment the property sets of streams with additional static information"
                module.version = "13.99.1"
    index: 4
        name: <module-switch-on-port-available>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "David Henningsson"
                module.description = "Switches ports and profiles when devices are plugged/unplugged"
                module.version = "13.99.1"
    index: 5
        name: <module-switch-on-connect>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Michael Terry"
                module.description = "When a sink/source is added, switch to it or conditionally switch to it"
                module.version = "13.99.1"
    index: 6
        name: <module-udev-detect>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Detect available audio hardware and load matching drivers"
                module.version = "13.99.1"
    index: 7
        name: <module-alsa-card>
        argument: <device_id="0" name="pci-0000_00_1b.0" card_name="alsa_card.pci-0000_00_1b.0" namereg_fail=false tsched=yes fixed_latency_range=no ignore_dB=no deferred_volume=yes use_ucm=yes avoid_resampling=no card_properties="module-udev-detect.discovered=1">
        used: 0
        load once: no
        properties:
                module.author = "Lennart Poettering"
                module.description = "ALSA Card"
                module.version = "13.99.1"
    index: 8
        name: <module-bluetooth-policy>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Frédéric Dalleau, Pali Rohár"
                module.description = "Policy module to make using bluetooth devices out-of-the-box easier"
                module.version = "13.99.1"
    index: 9
        name: <module-bluetooth-discover>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "João Paulo Rechi Vita"
                module.description = "Detect available Bluetooth daemon and load the corresponding discovery module"
                module.version = "13.99.1"
    index: 10
        name: <module-bluez5-discover>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "João Paulo Rechi Vita"
                module.description = "Detect available BlueZ 5 Bluetooth audio devices and load BlueZ 5 Bluetooth audio drivers"
                module.version = "13.99.1"
    index: 11
        name: <module-native-protocol-unix>
        argument: <>
        used: -1
        load once: no
        properties:
                module.author = "Lennart Poettering"
                module.description = "Native protocol (UNIX sockets)"
                module.version = "13.99.1"
    index: 12
        name: <module-default-device-restore>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Automatically restore the default sink and source"
                module.version = "13.99.1"
    index: 13
        name: <module-always-sink>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Colin Guthrie"
                module.description = "Always keeps at least one sink loaded even if it's a null one"
                module.version = "13.99.1"
    index: 14
        name: <module-null-sink>
        argument: <sink_name=auto_null sink_properties='device.description="Dummy Output"'>
        used: 1
        load once: no
        properties:
                module.author = "Lennart Poettering"
                module.description = "Clocked NULL sink"
                module.version = "13.99.1"
    index: 15
        name: <module-intended-roles>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Automatically set device of streams based on intended roles of devices"
                module.version = "13.99.1"
    index: 16
        name: <module-suspend-on-idle>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "When a sink/source is idle for too long, suspend it"
                module.version = "13.99.1"
    index: 17
        name: <module-console-kit>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Create a client for each ConsoleKit session of this user"
                module.version = "13.99.1"
    index: 18
        name: <module-systemd-login>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Create a client for each login session of this user"
                module.version = "13.99.1"
    index: 19
        name: <module-position-event-sounds>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Position event sounds between L and R depending on the position on screen of the widget triggering them."
                module.version = "13.99.1"
    index: 20
        name: <module-role-cork>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Lennart Poettering"
                module.description = "Mute & cork streams with certain roles while others exist"
                module.version = "13.99.1"
    index: 21
        name: <module-snap-policy>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Canonical Ltd"
                module.description = "Ubuntu Snap policy management"
                module.version = "13.99.1"
    index: 22
        name: <module-filter-heuristics>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Colin Guthrie"
                module.description = "Detect when various filters are desirable"
                module.version = "13.99.1"
    index: 23
        name: <module-filter-apply>
        argument: <>
        used: -1
        load once: yes
        properties:
                module.author = "Colin Guthrie"
                module.description = "Load filter sinks automatically when needed"
                module.version = "13.99.1"
    index: 24
        name: <module-x11-publish>
        argument: <display=:0 xauthority=/run/user/1000/gdm/Xauthority>
        used: -1
        load once: no
        properties:
                module.author = "Lennart Poettering"
                module.description = "X11 credential publisher"
                module.version = "13.99.1"
    index: 25
        name: <module-x11-cork-request>
        argument: <display=:0 xauthority=/run/user/1000/gdm/Xauthority>
        used: -1
        load once: no
        properties:
                module.author = "Lennart Poettering"
                module.description = "Synthesize X11 media key events when cork/uncork is requested"
                module.version = "13.99.1"
    index: 26
        name: <module-x11-xsmp>
        argument: <display=:0 xauthority=/run/user/1000/gdm/Xauthority session_manager=local/bobo-L450:@/tmp/.ICE-unix/1619,unix/bobo-L450:/tmp/.ICE-unix/1619>
        used: -1
        load once: no
        properties:
                module.author = "Lennart Poettering"
                module.description = "X11 session management"
                module.version = "13.99.1"
    index: 27
        name: <module-cli-protocol-unix>
        argument: <>
        used: -1
        load once: no
        properties:
                module.author = "Lennart Poettering"
                module.description = "Command line interface protocol (UNIX sockets)"
                module.version = "13.99.1"
1 sink(s) available.
  * index: 0
        name: <auto_null>
        driver: <module-null-sink.c>
        flags: DECIBEL_VOLUME LATENCY DYNAMIC_LATENCY
        state: IDLE
        suspend cause: (none)
        priority: 1000
        volume: front-left: 65536 / 100% / 0,00 dB,   front-right: 65536 / 100% / 0,00 dB
                balance 0,00
        base volume: 65536 / 100% / 0,00 dB
        volume steps: 65537
        muted: no
        current latency: 18,37 ms
        max request: 6 KiB
        max rewind: 6 KiB
        monitor source: 0
        sample spec: s16le 2ch 44100Hz
        channel map: front-left,front-right
                     Stereo
        used by: 0
        linked by: 1
        configured latency: 40,00 ms; range is 0,50 .. 2000,00 ms
        module: 14
        properties:
                device.description = "Dummy Output"
                device.class = "abstract"
                device.icon_name = "audio-card"
1 source(s) available.
  * index: 0
        name: <auto_null.monitor>
        driver: <module-null-sink.c>
        flags: DECIBEL_VOLUME LATENCY DYNAMIC_LATENCY
        state: RUNNING
        suspend cause: (none)
        priority: 1000
        volume: front-left: 65536 / 100% / 0,00 dB,   front-right: 65536 / 100% / 0,00 dB
                balance 0,00
        base volume: 65536 / 100% / 0,00 dB
        volume steps: 65537
        muted: no
        current latency: 0,00 ms
        max rewind: 6 KiB
        sample spec: s16le 2ch 44100Hz
        channel map: front-left,front-right
                     Stereo
        used by: 1
        linked by: 1
        configured latency: 40,00 ms; range is 0,50 .. 2000,00 ms
        monitor_of: 0
        module: 14
        properties:
                device.description = "Monitor of Dummy Output"
                device.class = "monitor"
                device.icon_name = "audio-input-microphone"
8 client(s) logged in.
    index: 0
        driver: <module-systemd-login.c>
        owner module: 18
        properties:
                application.name = "Login Session 2"
                systemd-login.session = "2"
    index: 4
        driver: <module-x11-xsmp.c>
        owner module: 26
        properties:
                application.name = "XSMP Session on gnome-session as 10941d20df5ef74c7158850018429356900000016190062"
                xsmp.vendor = "gnome-session"
                xsmp.client.id = "10941d20df5ef74c7158850018429356900000016190062"
    index: 5
        driver: <protocol-native.c>
        owner module: 11
        properties:
                application.name = "GNOME Shell Volume Control"
                native-protocol.peer = "UNIX socket client"
                native-protocol.version = "33"
                application.id = "org.gnome.VolumeControl"
                application.icon_name = "multimedia-volume-control"
                application.version = "3.36.1"
                application.process.id = "1663"
                application.process.user = "bobo"
                application.process.host = "bobo-L450"
                application.process.binary = "gnome-shell"
                application.language = "en_US.UTF-8"
                window.x11.display = ":0"
                application.process.machine_id = "eb257e4a9baa435b98e3417af120fbe0"
    index: 6
        driver: <protocol-native.c>
        owner module: 11
        properties:
                application.name = "GNOME Volume Control Media Keys"
                native-protocol.peer = "UNIX socket client"
                native-protocol.version = "33"
                application.id = "org.gnome.VolumeControl"
                application.icon_name = "multimedia-volume-control"
                application.version = ""
                application.process.id = "1727"
                application.process.user = "bobo"
                application.process.host = "bobo-L450"
                application.process.binary = "gsd-media-keys"
                application.language = "en_US.UTF-8"
                window.x11.display = ":0"
                application.process.machine_id = "eb257e4a9baa435b98e3417af120fbe0"
    index: 10
        driver: <protocol-native.c>
        owner module: 11
        properties:
                application.name = "gedit"
                native-protocol.peer = "UNIX socket client"
                native-protocol.version = "33"
                application.icon_name = "org.gnome.gedit"
                window.x11.display = ":0"
                window.x11.screen = "0"
                application.process.id = "3329"
                application.process.user = "bobo"
                application.process.host = "bobo-L450"
                application.process.binary = "gedit"
                application.language = "en_US.UTF-8"
                application.process.machine_id = "eb257e4a9baa435b98e3417af120fbe0"
    index: 11
        driver: <protocol-native.c>
        owner module: 11
        properties:
                application.name = "GNOME Settings"
                native-protocol.peer = "UNIX socket client"
                native-protocol.version = "33"
                application.id = "org.gnome.VolumeControl"
                application.icon_name = "multimedia-volume-control"
                application.version = "3.36.1"
                application.process.id = "3405"
                application.process.user = "bobo"
                application.process.host = "bobo-L450"
                application.process.binary = "gnome-control-center"
                application.language = "en_US.UTF-8"
                window.x11.display = ":0"
                application.process.machine_id = "eb257e4a9baa435b98e3417af120fbe0"
    index: 12
        driver: <protocol-native.c>
        owner module: 11
        properties:
                application.name = "Settings"
                native-protocol.peer = "UNIX socket client"
                native-protocol.version = "33"
                window.x11.display = ":0"
                window.x11.screen = "0"
                application.process.id = "3405"
                application.process.user = "bobo"
                application.process.host = "bobo-L450"
                application.process.binary = "gnome-control-center"
                application.language = "en_US.UTF-8"
                application.process.machine_id = "eb257e4a9baa435b98e3417af120fbe0"
                application.icon_name = "org.gnome.Settings"
    index: 13
        driver: <cli.c>
        owner module: 27
        properties:
                application.name = "UNIX socket client"
1 card(s) available.
    index: 0
        name: <alsa_card.pci-0000_00_1b.0>
        driver: <module-alsa-card.c>
        owner module: 7
        properties:
                alsa.card = "0"
                alsa.card_name = "HDA Intel"
                alsa.long_card_name = "HDA Intel at 0xf2500000 irq 29"
                alsa.driver_name = "snd_hda_intel"
                device.bus_path = "pci-0000:00:1b.0"
                sysfs.path = "/devices/pci0000:00/0000:00:1b.0/sound/card0"
                device.bus = "pci"
                device.vendor.id = "8086"
                device.vendor.name = "Intel Corporation"
                device.product.id = "293e"
                device.product.name = "82801I (ICH9 Family) HD Audio Controller"
                device.form_factor = "internal"
                device.string = "0"
                device.description = "Built-in Audio"
                module-udev-detect.discovered = "1"
                device.icon_name = "audio-card-pci"
        profiles:
                input:analog-stereo: Analog Stereo Input (priority 60, available: no)
                output:analog-stereo: Analog Stereo Output (priority 6000, available: no)
                output:analog-stereo+input:analog-stereo: Analog Stereo Duplex (priority 6060, available: no)
                off: Off (priority 0, available: unknown)
        active profile: <off>
        ports:
                analog-input-internal-mic-always: Internal Microphone (priority 8900, latency offset 0 usec, available: no)
                        properties:
                                device.icon_name = "audio-input-microphone"
                analog-input-mic: Microphone (priority 8700, latency offset 0 usec, available: no)
                        properties:
                                device.icon_name = "audio-input-microphone"
                analog-output-speaker-always: Speakers (priority 10000, latency offset 0 usec, available: no)
                        properties:
                                device.icon_name = "audio-speakers"
                analog-output-headphones: Headphones (priority 9900, latency offset 0 usec, available: no)
                        properties:
                                device.icon_name = "audio-headphones"
0 sink input(s) available.
1 source output(s) available.
    index: 0
        driver: <protocol-native.c>
        flags: DONT_MOVE 
        state: RUNNING
        source: 0 <auto_null.monitor>
        volume: mono: 65536 / 100% / 0,00 dB
                balance 0,00
        muted: no
        current latency: 0,00 ms
        requested latency: 40,00 ms
        sample spec: float32le 1ch 25Hz
        channel map: mono
                     Mono
        resample method: peaks
        owner module: 11
        client: 11 <GNOME Settings>
        properties:
                application.id = "org.gnome.VolumeControl"
                media.name = "Peak detect"
                application.name = "GNOME Settings"
                native-protocol.peer = "UNIX socket client"
                native-protocol.version = "33"
                application.icon_name = "multimedia-volume-control"
                application.version = "3.36.1"
                application.process.id = "3405"
                application.process.user = "bobo"
                application.process.host = "bobo-L450"
                application.process.binary = "gnome-control-center"
                application.language = "en_US.UTF-8"
                window.x11.display = ":0"
                application.process.machine_id = "eb257e4a9baa435b98e3417af120fbe0"
                module-stream-restore.id = "source-output-by-application-id:org.gnome.VolumeControl"
0 cache entrie(s) available. 

I'm getting this message for "sudo lspci -vv | grep -i audio"

"00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03)
        Subsystem: Toshiba Corporation 82801I (ICH9 Family) HD Audio Controller
pcilib: sysfs_read_vpd: read failed: Input/output error".

Also if at any interest the result of "aplay --list-devices":

**** List of PLAYBACK Hardware Devices ****
card 0: Intel [HDA Intel], device 0: ALC272 Analog [ALC272 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

The results for "lsmod | grep snd_hda_intel"

snd_hda_intel          53248  1
snd_intel_dspcfg       24576  1 snd_hda_intel
snd_hda_codec         131072  3 snd_hda_codec_generic,snd_hda_intel,snd_hda_codec_realtek
snd_hda_core           90112  4 snd_hda_codec_generic,snd_hda_intel,snd_hda_codec,snd_hda_codec_realtek
snd_pcm               106496  3 snd_hda_intel,snd_hda_codec,snd_hda_core
snd                    90112  12 snd_hda_codec_generic,snd_seq,snd_seq_device,snd_hwdep,snd_hda_intel,snd_hda_codec,snd_hda_codec_realtek,snd_timer,snd_pcm,snd_rawmidi

The result for dmesg |grep snd

[   17.862467] snd_hda_codec_realtek hdaudioC0D0: autoconfig for ALC272: line_outs=1 (0x14/0x0/0x0/0x0/0x0) type:speaker
[   17.862471] snd_hda_codec_realtek hdaudioC0D0:    speaker_outs=0 (0x0/0x0/0x0/0x0/0x0)
[   17.862473] snd_hda_codec_realtek hdaudioC0D0:    hp_outs=1 (0x21/0x0/0x0/0x0/0x0)
[   17.862475] snd_hda_codec_realtek hdaudioC0D0:    mono: mono_out=0x0
[   17.862476] snd_hda_codec_realtek hdaudioC0D0:    inputs:
[   17.862479] snd_hda_codec_realtek hdaudioC0D0:      Internal Mic=0x19
[   17.862481] snd_hda_codec_realtek hdaudioC0D0:      Mic=0x18


I don't know what else to try.