For me it isn’t working. Single player works fine. If Crossplay is ON I can see other games on the world map, but time out when joining the lobby. When I disable Crossplay I see none at all. (Yes, this is the opposite of what you might guess based on other issues people have mentioned where disabling Crossplay fixed it.)
Update: I switched to Proton 9 from the Cachy version and it works!
I know what you’re talking about, my condolences.
I had that bug too at times, and AFAIK it isn’t even Linux-specific; unfortunately, fixing it requires praying to all the gods you know of and hoping one of them hears your plight.
Here are some of the forbidden rituals I’ve had some success with:
If none of those work, which wouldn’t surprise me, I fear only time will fix your game as it did mine.
As for the anti-cheat being the cause: I don’t doubt for a second that it makes the netcode janky as fuck, but I have ~600 hours on record, and not more than 2 hours were on Windows 10. Linux’s fine.