On the question of the muted microphones issue, I found this:
https://github.com/jitsi/jitsi-meet/issues/5230
> Firefox sometimes does not send or receive any streams ... and leads to problems. That's why we put a notification when you are on Firefox and using meet.jit.si, to warn people.
So... fuck me I guess. Still no clue how to get Firefox to use the right microphone.
