There are many i915 warnings in dmesg.txt

Oct 19 14:33:05 kernel: ------------[ cut here ]------------
Oct 19 14:33:05 kernel: WARN_ON(is_mst && (port == PORT_A || port == PORT_E))
Oct 19 14:33:05 kernel: WARNING: CPU: 3 PID: 2246 at drivers/gpu/drm/i915/display/intel_ddi.c:3179 intel_ddi_pre_enable_dp.isra.0+0x20f/0x430 [i915]
Oct 19 14:33:05 kernel: Modules linked in: snd_usb_audio snd_usbmidi_lib hid_magicmouse cdc_ether usbnet cdc_acm hid_apple r8152 mii typec_displayport rfcomm ccm aufs cmac algif_hash algif_skcipher overlay af_alg bnep snd_hda_codec_hdmi binfmt_misc btusb btrtl btbcm btintel uvcvideo bluetooth videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_common ecdh_generic videodev ecc mc nls_iso8859_1 mei_hdcp snd_sof_pci snd_sof_intel_hda_common intel_rapl_msr snd_soc_hdac_hda snd_sof_intel_hda snd_sof_intel_byt snd_sof_intel_ipc snd_sof snd_sof_xtensa_dsp snd_hda_ext_core snd_soc_acpi_intel_match snd_soc_acpi snd_hda_codec_realtek snd_soc_core snd_hda_codec_generic snd_compress ac97_bus snd_pcm_dmaengine snd_hda_intel snd_intel_dspcfg dell_laptop x86_pkg_temp_thermal ledtrig_audio intel_powerclamp snd_hda_codec coretemp snd_hda_core snd_hwdep kvm_intel snd_pcm kvm snd_seq_midi snd_seq_midi_event crct10dif_pclmul snd_rawmidi ghash_clmulni_intel dell_wmi aesni_intel iwlmvm crypto_simd cryptd
Oct 19 14:33:05 kernel:  glue_helper snd_seq mac80211 dell_smbios snd_seq_device rapl dcdbas libarc4 intel_cstate snd_timer i915 snd input_leds serio_raw wmi_bmof dell_wmi_descriptor iwlwifi intel_wmi_thunderbolt rtsx_pci_ms hid_sensor_als hid_sensor_trigger drm_kms_helper industrialio_triggered_buffer kfifo_buf hid_sensor_iio_common industrialio mei_me memstick i2c_algo_bit 8250_dw fb_sys_fops ucsi_acpi soundcore processor_thermal_device joydev syscopyarea typec_ucsi intel_rapl_common mei cros_ec_ishtp cfg80211 hid_multitouch sysfillrect cros_ec sysimgblt intel_soc_dts_iosf mac_hid typec int3403_thermal int340x_thermal_zone intel_hid sparse_keymap int3400_thermal acpi_thermal_rel acpi_pad acpi_tad sch_fq_codel parport_pc ppdev lp parport drm ip_tables x_tables autofs4 wacom usbhid hid_sensor_hub hid_generic intel_ishtp_loader intel_ishtp_hid rtsx_pci_sdmmc crc32_pclmul psmouse nvme intel_ish_ipc intel_lpss_pci intel_ishtp i2c_i801 intel_lpss rtsx_pci nvme_core thunderbolt idma64 virt_dma wmi i2c_hid
Oct 19 14:33:05 kernel:  hid video pinctrl_icelake pinctrl_intel
Oct 19 14:33:05 kernel: CPU: 3 PID: 2246 Comm: Xorg Tainted: G        W         5.4.0-51-generic #56-Ubuntu
Oct 19 14:33:05 kernel: Hardware name: Dell Inc. XPS 13 9300/0WX9VX, BIOS 1.2.0 08/13/2020
Oct 19 14:33:05 kernel: RIP: 0010:intel_ddi_pre_enable_dp.isra.0+0x20f/0x430 [i915]
Oct 19 14:33:05 kernel: Code: ff ff 83 f8 0a bf 00 00 00 00 49 0f 44 fc 48 89 7d c0 e9 4b fe ff ff 48 c7 c6 e0 9a b3 c0 48 c7 c7 43 09 b5 c0 e8 ec 34 e0 fa <0f> 0b e9 ae fe ff ff 41 8b 54 24 70 8b 75 a8 4c 89 e7 e8 8a c7 ff
Oct 19 14:33:05 kernel: RSP: 0018:ffffb14242a1f810 EFLAGS: 00010282
Oct 19 14:33:05 kernel: RAX: 0000000000000000 RBX: ffff9fa3a3dbf000 RCX: 0000000000000000
Oct 19 14:33:05 kernel: RDX: 0000000000000035 RSI: ffffffffbd3955d5 RDI: 0000000000000246
Oct 19 14:33:05 kernel: RBP: ffffb14242a1f868 R08: ffffffffbd3955a0 R09: 0000000000000035
Oct 19 14:33:05 kernel: R10: ffffffffbd395980 R11: 00000000bd39559f R12: ffff9fa3a3dbf000
Oct 19 14:33:05 kernel: R13: ffff9fa24d8fc000 R14: ffff9fa3a93c0000 R15: ffff9fa3a3dbf120
Oct 19 14:33:05 kernel: FS:  00007f3f76e0fa80(0000) GS:ffff9fa3af6c0000(0000) knlGS:0000000000000000
Oct 19 14:33:05 kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Oct 19 14:33:05 kernel: CR2: 00007f3f6c2ec000 CR3: 000000084ff46004 CR4: 0000000000760ee0
Oct 19 14:33:05 kernel: PKRU: 55555554
Oct 19 14:33:05 kernel: Call Trace:
Oct 19 14:33:05 kernel:  ? intel_set_cpu_fifo_underrun_reporting+0x89/0x2a0 [i915]


The function "intel_ddi_pre_enable_dp" has changed significantly from 5.4 to 5.8. You can try 5.8 kernel (https://people.canonical.com/~alexhung/LP1900377/groovy/, used in 20.10 and perhaps future 20.04.2) or latest 5.9 mainline (https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.9.1/)