I am pleasantly surprised how good combo Debian sid / Steam Beta / Proton Experimental has been for gaming (converted from OS X for different reasons and then discovered the gaming experience is great too)
Valve could have tried to cater to the Android/NDK folks to also support native GNU/Linux, and do some nudging into cross platforms APIs like Apple is doing with the game porting kit, instead they chose to solidify DirectX/Windows as the main APIs PC game developers care about.