This is apparently due to conflicts with anti-cheat software which leave you unable to log into some multiplayer servers, however, Valve are committed to improving Proton’s compatibility, and the Steam Deck will also be running a new, and hopefully improved, version of SteamOS. Apex Legends, Destiny 2, Tom Clancy’s Rainbow Six Siege on Valve’s new handheld PC. This means that unless something changes, you won’t be able to play Playerunknown’s Battlegrounds. In a report by ProtonDB, a database detailing just what Proton can do, it’s revealed that almost half of Steam’s top ten most played games aren’t available through the software. While Valve’s Proton software, which the Steam Deck will be running as a compatibility layer to play a number of Windows games that don’t have official Linux versions, is very impressive, it’s not a universal solution to the problem of gaming on Linux.

While Valve’s Steam Deck will be able to support modded games as well as virtually any software which is compatible with SteamOS’s Linux base, you won’t be able to play some of Steam’s most popular games.

How to mod a steam game