

As someone else mentioned, keyboard buttons need mapping to controller
As per my other contribution, I tried other proton versions to solve the stutter loading new sections and thought I'd fixed it. However, the stutter returned in the later worlds, then I realised it has a native Linux version listed at the bottom of the "Force compatibility tool" list in the game's properties, titled "Steam Linux Runtime", problem solved.
Tried with Proton Experimental, 7.0-3 and 6.3-8, all had freezes/stutters loading new sections, sometimes crashing the deck. No problems with GE
By default keys are mapped to some keys you have access to only on a keyboard - which is not great for Steam Deck. I had to map these to my buttons. The joystick part was great out of the box. After that works great!