The problem occurs somewhat sporadically, and sometimes plugging a speaker in after boot-up is accepted, but I just want to know how I can get the computer to register sound devices after start up. It should be possible, because when the computer booted up with a speaker connected, I can take the speaker out and switch them around, and it still works (most of the time). The problem has been going since 20.04, and stopped completely for a brief period after updating (I think, but the sporadic nature makes it hard to tell).
While I would like to know the cause, I really just want to know how to get the speaker noticed by the computer without restarting, no matter how messy it is.
