After upgrading to ubuntu 20.04 the hdmi sound stopped working. If I select headphones as audio output they work well, but if I change to HDMI output it doesn’t work.
I did this and it solved the problem:
rm -r ~/.config/pulse/
reboot
If I would have read further, I could have resolved it without needing to reboot:
killall pulseaudio; rm -rf ~/.config/pulse/* ; rm -rf ~/.pulse*
Source: https://askubuntu.com/questions/1230002/hdmi-sound-not-working-after-upgrading-to-20-04