May I ask you if you’re using a 6+ kernel?
Briefly: I’ve faced a very similar problem with HDMI audio since kernel 6x:
Not really solved it yet, but found a workaround using linux-rt-lts kernel, which is still a ‘5.15.96.61’:
sudo pacman -S linux-rt-lts linux-rt-lts-headers
sudo grub-mkconfig -o /boot/grub/grub.cfg
Ref:
-
No audio - pulsemixer Dummy Output after kernel update 6.1.12-1-lts: Module snd_hda_intel_codec not found in directory /lib/modules/6.1.12-1-lts - #11 by storm
and - Audio assente dopo aver installato Endeavouros KDE Cassini Nova 03-2023 - #2 by storm
My educated guess for now is ‘blame it on kernel 6*’.
Hope this can help,
Piero