(I had originally necroposted to another post but then decided to post separately since my issue is a little different: My internal microphone doesn't work (ZORIN OS LITE )!)
I'm having an internal mic issue with Zorin OS Lite 16.2 on an old Acer C720P Chromebook.
The Sound Recorder seems to want to use the "Monitor" for the microphone but it doesn't work. But I get audio detection if I choose the "Microphone (unplugged)" option instead of the "Internal Microphone" option. Weird.
Another weird thing is that I can't set the Internal Microphone as a fallback device only - it always chooses the monitor of the device as well.
I tried making the alsamixer adjustments noted in the post above (Mic Boost, Capture, Internal Mic Boost all at 100 and not muted). I tried setting the left channel of the "Internal Microphone" to use the right channel only and vice versa.
I also tried adding "model=auto" to the options line in the alsa-base.conf and rebooted.
The only thing that seems to work is if I start a recording, then quickly flip to pavucontrol and change the input to "Built-in Audio Analog Stereo" instead of "Monitor of Built-in Audio Analog Stereo". This is not practical for things like Zoom and such.
I think if the "Monitor of..." option was not present, it might work but I don't know how to delete such entries.