Sure, this comic edit is just for the fun of it

Easiest way is to use heroic. You can easily install it from the discover store, log in with your gog account and click install. Then right click and add to steam directly from the heroic interface, this way it will show up in the deck game mode.

Ps: I know you wrote you don’t need a fancy launcher, but this is legitimately the absolute easiest way to go about it.