I've been playing Company of Heroes base game via Steam play (Proton + DXVK) for ages on Manjaro with both multiplayer and single player and working fine.
I'm using NVIDIA driver 415.18 for Linux and I'm unsure of which version of Proton is running currently.
I saw Eastern front and I thought I'd give it a go.
First issue encounter was that it just won't launch with steam play and if you launch it with wine then it'll complain about steam not running. To fix this I found a thread that gave the launch options dev -mod ef_beta -nomovies for the base game which allows me to run Eastern front.
Single player works perfectly fine however when I try playing multiplayer with a friend that runs Windows, I cannot see them in my friends list unless they run the base game with the same launch parameters.
Now the real problem is that we cannot enter a match because the game instantly crashes to desktop for me but doesn't crash for my friend. The loading bar will fully complete and when it's time to move past the loading screen, instant crash.
I'm having a hard time finding any sort of dmp file in the wine directory but I've attached logs that may or may not be helpful.