Since updating to 5.10.16 switching between speakers and headphones through alsamixer on my Sound Blaster Z does nothing. it doesn't seem to send any error messages on log either.
What was the last working version? And if you boot that kernel version while keeping the rest, it starts working again?
Turns out if i shutdown my system unplug it from the wall and hold down power for a few seconds and boot again it works fine again. This isn't a completely new behavior, on kernel<5.10 it used to be that if i didn't do this i wouldn't get any sound at all, now its unable to change output and some of the post processing effects from the card are screwed up as well, none of this is necessary when i boot on Windows, but it isn't really a regression either. if you could point me at the right documentation to try poking at it, I'd love to try and fix this.
so i recently did some changes on my system's hardware and thought my psu might be getting overwhelmed and upgraded it. turns out since then this problem is gone.