ProtonDB collects reports from gamers running Steam games under Valve’s Proton compatibility layer designed to allow Windows games to run on Linux.
Steam Play now officially supports a limited but growing set of ‘whitelisted’ games that are deemed Proton-compatible and play on Linux. Based on ProtonDB reports, a significant number of non-whitelisted games, including many popular titles, play just as well as on Windows.
Valve’s upcoming Steam Deck will rely on Proton to run Windows games, and ProtonDB is one of the best resources I’ve found for checking which games work (or not) on Proton.