The game is not out yet, and the playtest is no longer up. So you wouldn't be able to play anyway, but in the future you can change your microphone settings. The game defaults to "open mic" but I recommend putting it on "push to talk" if you plan on chatting on discord at the same time. You can do this both in the settings, and in the pause menu by pressing LB on your controller (not sure what the mnk input is, but it should be shown on screen anyway)