Internal speaker (Audio) is not working in Ubuntu 20.04

Your ALSA have loaded snd_acp3x_rn module, but card was not recognized fully, unlike snd_hda_intel. Since you are using dual boot, the problem can be ‘Fast Startup’, that puts hardware into a hybrid hibernation state instead of a full shutdown. Disabling Fast Startup is a must when dual-booting. Shutdown.

The origin of this hint is here: https://forum.manjaro.org/t/sound-from-speakers-no-sound-from-3-5mm-jack-audio-amd-thinkpad-e595/13717/6

EDIT: another idea. There can be wrong module loaded for your sound card. Try to blacklist the following modules in /etc/modprobe.d/blacklist.conf:

    blacklist snd_acp3x_rn
    blacklist snd-acp3x-pdm-dma
    blacklist snd-acpx-rn
    blacklist snd-rn-pci-acp3x

Blacklist them one-by-one, reboot after each. Check the result with aplay -l.