Hi there Mozilla : you can add to Options "Set Audio Devices :" and just allow the user set Input / Output devices indepentment ?
---Unnecesary explaniation of my particular case : ---
i am Slackware64 14.2 user, until the past week, i had my operating system just with ALSA (Advance Linux Sound Arquitecture), but when i upgrade Firefox to latest version, Firefox or simple not have audio output, or directly hang the operating system.
Well the case was Firefox force to my to install a software i really hate like PulseAudio, you for try had Audio Output when i watch online videos.Well i try to watch youtube videos, and when the video is muted, the playback works, but if i enable Audio, the video just stop, Firefox can't Play it, i must download the video and after watch with a video player of my operating system for watch the video i want to see online before just Firefox don't have options for set Audio Input/Output devices. my pc had 2 Sounds Cards, the integrated, is burned too much years ago but the system detect like not had problem, well i blocked in module levels using the blacklist for block that soundcard and just use the pci sound card.
The thing is riht now i had delete manually the "$HOME/.mozilla" folder, start from scrath, like too much sites says, to solve the problem, the thing is that don't revolve the issue for me, the problem persist, looks like had firefox had a problem with audio device, but i don't now how i can log a debug trace for report to mozilla and solve this problem, because looks like is common from Firefox 58.0 and still in Firefox 108 is present.
Just for that i think a possible solution is just let the user set the audio devices input/output, using only ALSA i had never before was problem with video/audio playback
except firefox can't use a GNU/Linux just with real ALSA. which is part of kernel, is senseless force the user change to PulseAudio when that is a optional audio server and remove the real alsa support, and is senseless does not allow users to set manully the audio devices, searching i found one or two articles with a very complex process of make work and usb sound card under GNU/Linux if your default browser is firefox. The rest during 7 years all related with audio/video works fine on my operating system, just four days with pulseaudio and start the problems.