I've seen many posts on the Steam discussion forum of people having problems getting online play working. Here's the fix. https://steamcommunity.com/sharedfiles/filedetails/?id=2800936441
Thanks to @WAZAAAAA if it weren't for him / her I wouldn't be playing today!
Install the game. Once installed right click the game in your library and choose properties. Choose compatibility and select Proton 4. 2-9
Right click the game again in your library and choose properties and pick general. Enter the following into Launch Options. PROTON_NO_ESYNC=1 %command%...
