Ubuntu “Dummy output” No sound card in use

I ran into this exact same issue on my issue. I don’t know if you are experiencing the same problem because it ended up being that timidity-daemon was causing this to appear. I ended up having to remove that and it started working.

The one thing I can suggest as a workaround is running this command

sudo alsa force-reload

This would force my device to start working again.

source https://askubuntu.com/questions/1242766/ubuntu-20-04-dummy-output-no-sound-card-in-use