firefox 75 pulseaudio sound suddenly stopped working

["007@caiway.net" <007@caiway.net>]

Hi,

On my debian stable firefox 75 the sound stopped working.

Another user does have sound on stock firefox.

I can not go back to stock firefox, my profile of firefox 75 can not be
loaded any longer.

7 Chapters of troubleshooting pulseaudio did not help me in 4 hours:
https://wiki.archlinux.org/index.php/PulseAudio/Troubleshooting

Another thing from this guy Pottering does not give any hint:

journalctl -f 
journalctl -f | grep pulseaudio

nothing

pulsemixer does seem to be alright:
firefox: AudioStream is showing up, I can select it, and set volume (but
no sound).

but:
$ pactl list sink-inputs 
no output at all

$ pacmd list-sink-inputs 
0 sink input(s) available.


I am left clueless.
(no timidity here installed.
alsamixer shows the pulseaudio interface, unmuted)

[
I hate pulseaudio since when I had a linux terminal server project LAN.
In those days pulseaudio fucked up all LAN audio playing.
]

Waterfox and Palemoon browsers both play audio well.

Hope someone can give a hint

Thanks 4 reading