Surprisingly, Rockstar have now added BattlEye anti-cheat to Grand Theft Auto V / GTA Online, and sadly it seems they have not enabled the support for Linux desktop and Steam Deck with Valve's Proton. ARTICLE UPDATED.
So I wonder what my copy from rockstar will do now, it worked like a week ago under wine(single player). I bought it before it was available on steam unfortunately.
That said gta online was never good so idgaf about that part but Battle eye isnt going to do shit so sucks for those that do care.