Upgrade to 10 from 9 - audio/sound not working at first but solved it (pulseaudio/alsa/timidity)

TLDR?

apt purge timidity timidity-daemon # worked for me

The upgrade from Trisquel 9 to 10 was smoother for me than 7 to 8 or 8 to 9.

One thing I did differently was to make sure apt/dpkg were in a happy state before rebooting. In other words, I used the suggested "auto remove" and "fix broken" apt commands, did several iterations of upgrade and autoremove, and did not reboot until zero packages needed updating and zero complaints from aptitude.

After the upgrade, audio or sound were not working. I could see the various "snd" kernel modules related to my hardware and no alarming messages in syslog. I saw some suggestions online to "apt reinstall alsa-base pulseaudio" and then "alsa force-reload" which worked the first time but not after a reboot. I tinkered with reinstalling other packages related to pulseaudio. Pulseaudio would be running and the PulseAudio Volume Control would open, but it would show no hardware devices. One of the times that a run of "alsa force-reload" recovered audio I noticed it mentioned two processes it killed. One of them was pulseaudio as expected but I wondered what the other was.

As it turns out, timidity and timidity-daemon had been installed in the past, and timidity was running prior to pulseaudio (pid 9xx), then pulseaudio starts per session, but perhaps timidity had already taken the sound device via alsa or something like that. The solution for me was to "apt purge timidity timidity-daemon" because even after uninstalling only the daemon package it will leave some init/systemd scripts lying around. There is probably a more nuanced solution for those who want to use timidity.

I thought I would share in case anyone else had the same issue.