The new Star Wars Xcom game says it's unsupported on Deck and Machine. I know those aren't always entirely accurate. I didn't suppose anyone's gotten the game and tried it have they?
With Steam Input you an play with gamepad, even if they don't support gamepad. Either the community made a configuration you can easily download and apply, or you can create yourself one. But that is not convenient and straight forward like an official gamepad support for sure.