Fixing Linux Audio, Spring '21 edition

When upgrading from Ubuntu 20 to 21 this spring, my father and I both had the rear audio line out on our computers stop working. As we both had the same problem, I figured I would write it up in case anyone else was affected.

Symptoms

1. The original audio device no longer shows up in the list of audio devices.
2. The device is not turned off or muted, and cannot be turned on or unmuted, because it doesn't exist any more.
3. Other devices (USB headphones, Bluetooth, etc.) still work.
4. When no other audio device is attached, a dummy audio device is created.
5. The troublesome audio device shows up when running some commands, I think such as pacmd list-sinks.

Confirmation

1. Running sudo lsof /dev/snd/* in a console shows Timidity holding open some files.
2. Ending the timidity process makes the audio device show up again.

Fix

1. Uninstall Timidity using your software manager, or by running sudo apt remove timidity.

Somewhat surprisingly, this does not seem to affect my ability to play back Midi files. I assume my music program is using Fluidsynth, which is a separate system? Nonetheless, a strange bug caused by a misconfiguration somewhere.

tags: linux, sound, audio, fix, tech support, workaround