Kubuntu 20.04.1 (Lenovo P50): Built-in audio not found after release upgrade

[estolle]

After having had a smoothly running Kubuntu 18.04.5 I migrated to Kubuntu 20.04.1 just three days ago. Today I wanted to start a Zoom web meetingwhen Zoom reported that it could not find my internal microphone. This was the first time I was trying to use the microphone after the release upgrade. The system settings reports the same ("no recording devices available").

The system settings provides interesting information. As my laptop is equipped with Nvidia QuadroM1000M, I was able to choose between different combinations of input and output profiles in system settings - Audio - Advanced.

However, now there are only profiles available which are related to the audio controller onboard the Nvidia chipset. The others are missing (Stereo input, Mono input, Stereo output etc.).

But I still can start a Zoom meeting and can hear and see everything. This is due to the fact that the output is using the audio chipset of the Nvidia Quadro.

Using an external webcam (Logitech Webcam Pro 9000 Mono) I am able to transmit a Mickey Mouse type of sound. This webcam worked well before the release upgrade.

Last but not least, I tried using a bluetooth headset which I am able to connect flawlessly but it won't help either.

I found a similar bug in
https://askubuntu.com/questions/1230283/internal-micrphone-is-not-working-in-ubuntu-20-04

so I tried the proposed

pulseaudio -k && sudo alsa force-reload

but it won't work. So I believe there is something wrong with the kernel.

Output of inxi -Fxxxz

System: Kernel: 5.4.0-48-generic x86_64 bits: 64 compiler: gcc v: 9.3.0 Desktop: KDE Plasma 5.18.5 tk: Qt 5.12.8 wm: kwin_x11 dm: SDDM Distro: Ubuntu 20.04.1 LTS (Focal Fossa)

Machine: Type: Laptop System: LENOVO product: 20EN0005GE v: ThinkPad P50 serial: <filter> Chassis: type: 10 serial: <filter> Mobo: LENOVO model: 20EN0005GE serial: <filter> UEFI: LENOVO v: N1EET86W (1.59 ) date: 08/28/2019

Audio:
Device-1: Intel 100 Series/C230 Series Family HD Audio vendor: Lenovo driver: snd_hda_intel v: kernel bus ID: 00:1f.3 chip ID: 8086:a170
Device-2: NVIDIA GM107 High Definition Audio [GeForce 940MX] driver: snd_hda_intel v: kernel bus ID: 01:00.1
chip ID: 10de:0fbc
Sound Server: ALSA v: k5.4.0-48-generic

***
Output of dmesg | grep snd

[ 4.678462] snd_hda_intel 0000:01:00.1: enabling device (0000 -> 0002)
[ 4.678530] snd_hda_intel 0000:01:00.1: Disabling MSI
[ 4.678535] snd_hda_intel 0000:01:00.1: Handle vga_switcheroo audio client
[ 4.711131] snd_hda_codec_realtek hdaudioC0D0: autoconfig for ALC298: line_outs=1 (0x14/0x0/0x0/0x0/0x0) type:speaker
[ 4.711133] snd_hda_codec_realtek hdaudioC0D0: speaker_outs=0 (0x0/0x0/0x0/0x0/0x0)
[ 4.711134] snd_hda_codec_realtek hdaudioC0D0: hp_outs=2 (0x17/0x21/0x0/0x0/0x0)
[ 4.711135] snd_hda_codec_realtek hdaudioC0D0: mono: mono_out=0x0
[ 4.711135] snd_hda_codec_realtek hdaudioC0D0: inputs:
[ 4.711136] snd_hda_codec_realtek hdaudioC0D0: Mic=0x18
[ 4.711137] snd_hda_codec_realtek hdaudioC0D0: Dock Mic=0x19
[ 4.711138] snd_hda_codec_realtek hdaudioC0D0: Internal Mic=0x12
[ 19.795557] snd_hda_codec_hdmi hdaudioC1D0: HDMI: invalid ELD data byte 61
[ 5114.913448] usbcore: registered new interface driver snd-usb-audio

Just for sake of completeness the inxi output
Graphics:
Device-1: NVIDIA GM107GLM [Quadro M1000M] vendor: Lenovo driver: nvidia v: 450.66 bus ID: 01:00.0 chip ID: 10de:13b1
Display: x11 server: X.Org 1.20.8 driver: nvidia unloaded: fbdev,modesetting,nouveau,vesa compositor: kwin_x11 resolution: 2560x1440~60Hz, 1920x1080~60Hz
OpenGL: renderer: Quadro M1000M/PCIe/SSE2 v: 4.6.0 NVIDIA 450.66 direct render: Yes

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 5.4.0-48.52-generic 5.4.60
Uname: Linux 5.4.0-48-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu27.9
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Fri Oct 2 13:02:31 2020
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/kubuntu.seed boot=casper maybe-ubiquity quiet splash ---
InstallationDate: Installed on 2019-06-07 (483 days ago)
InstallationMedia: Kubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
SourcePackage: ubiquity
Symptom: installer
UpgradeStatus: Upgraded to focal on 2020-09-29 (2 days ago)