It is the anti-cheat. People have gotten the game to run via Proton, however you simply can’t join lobbies no matter what be because of the anti-cheat. It would just be a matter of Epic enabling support for Linux/Proton in EAC on their side, however Epic has publicly been against doing so stating some pretty nonsensical reasons to why they choose not to enable support.
It is the anti-cheat. People have gotten the game to run via Proton, however you simply can’t join lobbies no matter what be because of the anti-cheat. It would just be a matter of Epic enabling support for Linux/Proton in EAC on their side, however Epic has publicly been against doing so stating some pretty nonsensical reasons to why they choose not to enable support.