There's a utility app on macOS that I've used for years called Shush < https://mizage.com/shush/ > that provides a global mic toggle (double tap to invert toggle to speak/mute).

Very nice because it works at OS level and is same no matter which app I'm using.

In gnome, I'm using the "nothing-to-say" extension for this: https://github.com/wbolster/nothing-to-say

Hm, I know pulse audio has a CLI that allows muting, you could probably hack something up in Bash, maybe with netcat to get messages from a keyboard daemon to the script.