Flatpak – Batocera Nation
That link has all the instructions to get you started. Once you get Steam installed you have to go to the settings and go to ‘Steam Play’ and then ‘Enable Steam Play for Supported Titles’ and ‘Enable Steam Play for all other Titles’.
EVERY game in your steam library will become available to download. MANY games I’ve tested have worked perfectly, and many that don’t work over WineHQ. I’ve personally tested: Batman: Arkham City GOTY, Bioshock Infinite, Bloodstained: Ritual of the Night, Borderlands 2, Catherine Classic, Doom (2016), Skyrim, Metal Gear Solid 5: The Phantom Pain, Resident Evil 4, Super Meat Boy and Valkyria Chronicles. I haven’t gotten Persona 4 Golden and Batman Arkham Asylum to work yet.
This is using the technology that will allow games to run on the Steam Deck once it releases. It’s pretty good, but I’m guessing by launch of the Steam Deck it will be almost flawless.