Speaking in a voice channel/voice call in the Linux desktop app causes the volume of my mic to lower by itself

Most other voice applications I've used handle autogain internally, like as an effect applied on a copy of the audio source.

If these other applications that you're thinking of are not using WebRTC, then that would be why. As I mentioned, this is a known behavior for WebRTC applications like Discord and Fluxer when using automatic gain control. It automatically lowers the microphone volume at the system-level on both Windows and Linux. I don't have a Mac, but I'd assume it acts the same unless Mac doesn't allow access to its system audio API in this way. https://wiki.robotz.com/index.php?title=WebRTC_Automatic_Gain_Control Edit: formatting