Okay, after making changes to my ALSA settings (namely, specifying a model rather than leaving it auto), I have things set up so that analog 5.1 surround is able to be properly output to with, say, aplay or speaker-test — the device that should correspond with it does. However, pulseaudio is still reporting it as "unplugged", which I believe is causing problems. Things that have an over-ride to specifically output through analog does fine, but even if I set it as the default output in /etc/pulse/default.pa, it can't actually be treated as a default for thesystem in general. At best, I can manage this by manually switching over the output in pulseaudio Volume Control for each app, and it still doesn't show as an option in System Settings –> Sound. If it matters, I have ALC889 on-board audio, and I'm using 16.0.4.1 LTS with its default kernel.
Ubuntu – Pulseaudio incorrectly reporting analog 5.1 as unplugged
pulseaudiosound
Best Answer
Finally solved it. I had one speaker jack in a port that was working, but technically wasn't actually the "right port", and because of the way pulseaudio detects line out status, that made it detect the speakers as unplugged.