itch.io

You can,  once you add it as a none steam game in desktop mode you switch back to the “big picture” boot the game up then press the steam button and go to controller setting and remap keys, I managed  to get the back buttons to work as key presses for the game [ what I did:  GAMEPAD WITH JOYSTICK TRACKING/ edited L4 to SPACE scroll down and toggled enable back grip buttons, returned to the game and it worked for me even the face buttons worked ]