Nouveau driver gave terrible FPS. Nvidea open source driver works great.

The game incorrectly thinks my PC can only handle potato graphics settings, defaults to minimal graphics, and warns me not to play multiplayer with >4 players. If I ignore the warnings and set the graphics to high it works great. No FPS issues.

If you want to copy your keybind config from windows, the location is: ${YOUR_STEAM_DRIVE}/steamapps/compatdata/1466860/pfx/drive_c/users/steamuser/Documents/My Games/Age of Empires IV/keyBindingProfiles/