I don’t know why this is marked incompatible with the steam deck. I played the entire game on the original steam deck model using the controls layout that valve automatically picked to be best compatible.

I went into the settings and set the options to fullscreen. According to comments within discussion threads, this is something that you have to do to prevent the game from running at half its speed. The game still had slow down very occasionally, but only when they were a lot of enemies on the screen or when I was in specific parts of specific rooms.

I do not feel that hampered my experience at all, and I would easily recommend the game to anyone that enjoys the series or to any newcomers looking for a platformer they can beat within a day.