What Proton is
Proton is Valve’s compatibility layer, built into Steam. It lets Windows games run on Linux and the Steam Deck without a Windows install: you click Play and Steam handles the rest. It builds on Wine and translates DirectX graphics to Vulkan.
There is no complete list of “every Proton game”: Proton runs tens of thousands of Steam games, and it changes with every update. So we took the 100 games people are actually playing right now and checked each one against three sources: Steam (does it have a native Linux version?), ProtonDB (how well does it run?) and Valve’s Steam Deck rating.