I’ve looked at suggestions on StackExchange and made some changes to files in /etc but after each login or reboot it is up to 100 % again in pavucontrol. On this computer I hardly ever use the speakers, and I want the microphone muted, always, so I guess I could even block list a few kernel modules for sound (which ones ?). But why can a desktop user not easily turn volume to zero, forever ?
Edit : Thanks all. It was not StackExchange but on AskUbuntu from where I tried some suggestions. I also tried muting audio in Pavucontrol but that didn’t help between logouts and logins. Now I have set the default audio device in Pavucontrol to Dummy, and that works. I can still play sound from a video in VLC, but the microphone keeps muted.
That’s strange.
I mute my microphone (its input volume is at 100%, just muted). But it always stays muted until I unmute. Even between logins and reboots. I do use pipewire, so there’s a difference. But I believe pulseaudio did the same for me back in the day.
One solution could be to mute the microphone in your DE or WM initialization file. Which are you using? Gnome? i3 perhaps? You could use pactl to mute the microphone on each login.
Let me know if you need further assistance.