Comment by killdozer

You don't even have to do any of this, you can compile for windows and use the SDK (once you've enabled developer mode in the steam deck settings and paired) (https://partner.steamgames.com/doc/steamdeck/loadgames) to add your packaged game as a new title. I've compiled and tested games from unreal 4 and Godot 3.something without issue using proton. Using the SDK vs ssh is really nice since it shows up in Steam automatically and updating is easy (just redeploy via the SDK). Be warned the SDK is windows only.