As has been noted in other examples below, the game has no mic selecting function and reverts to the "Windows default microphone". In practice for me, going into PulseAudio and setting my mic to the Fallback option under input devices worked.

It also has a very low preset volume for ingame chat, so expect to need to bump your ingame mic volume and boost other players volumes for the game to be playable

This is a common problem to Windows users as well, for some reason the game won't recognise button's mapped to a mouse for use specifically with the push to talk. It will allow you to map it and then not register an input. The game does allow mapping anything else to mouse buttons without issue

Again a problem Windows users also have, the game will occasionally crash when loading into a match. While playing with friends, it usually happens to at least one or two people over the course of a session. It does however allow for hot-joining back in so no reset to lobby required unless the host crashes.