So, after weeks of trying I got so far as to be able to run Wildlands on about any proton from valve 6.3 up to ge-19-2 (ge-20-1 crashes at intro). And all from lutris-14-4 up also at least don't cause "no online" bug as valve 6.3 does.
But: I'm not able to play with others. As soon as I join someone else ... or someone joins me ... I get kicked to menu with text "kicked by eac (anticheat)".
But: A friend of mine runs it quite well for at least back when Predator went live. So it's sure possible and although I copied his system as best I could I keep getting kicked by anticheat while we can play together when I'm on windows.

Any help?