Looks like NixOS's pipewire service enables WirePlumber by default. Not sure if it changed recently from media-session, and that's why it's gone unstable, or if it's something else.
I've run into a similar issue, where the default output device wouldn't be selected, when I used PulseAudio by itself before Pipewire was a thing. I had to use one of the PA console mixers to set my default output and input devices, and with some playing around with it, I was able to make them the default. Might help to use pactl or one of the many PA mixers to poke around and see if there's anything you can adjust to fix the issue.
Might also help to test out pipewire-media-session to see if that helps, too.
When I was futzing around two or three months ago with audio on my NixOS system I believe it was still using media-session. Are you on unstable? I believe the intention was to migrate to WirePlumber, but didn't expect that to happen already.
Yeah, if it works with the PA tools, then you're using pipewire-pulse. If you aren't using WirePlumber, try it out, as pipewire-media-session doesn't work as well and is more of a reference implementation than an end-user product.
I found when Fedora switched to wireplumber it made bluetooth much less reliable. Every time I connected my headphones I had to restart wireplumber multiple times for them to connect. Haven't tried it for a few months though, maybe it's improved.
I have the same issue on the latest Fedora. It's very disappointing that bluetooth connectivity isn't a solved problem in 2022 (at least on Linux, haven't noticed any issues in Windows for a while). Are we ever going to get to a point where bluetooth "just works"?
I have daily bluetooth issues on Windows. Someone decided it was a good idea to have bluetooth jabra speakers/microphones for our meetingrooms... It takes 5 minutes to do the pair/connect/set correct device dance... every. day.
My macbook can't even figure out that it should try to connect to my offce trackpad after I have had it connected to my home trackpad! Thankfully it has a built in trackpad that I can use to manually connect when the "automation" fails..
I had a 12" MacBook no-adjectives in the past which didn't even work with AirPods well. I was hoping the M1 would have a better BT stack (the iPhone's...)
Yeah, I've just been restarting the pipewire service instead of looking into it, but I started having audio output fail when I switched to wireplumber.
Wireplumber looks much more wonky to me than media-session, so I'm deferring the switch for now. Wireplumber's design seems flashy and not guided by experience or good taste to me, the opposite of Pipewire proper.
It turns out that Nix Unstable switched from media-session to WirePlumber recently and that is the source of the instability I'm seeing. Perhaps it's not yet configured properly in Nix.
