This should be effectively fixed if a steam.inf that contains:AppID=215 is created in the mod folder.
This applies for Windows too. although this latter only applies to connecting clients, not listen servers.
And this specific case seems to be when hosting a listen server.
Source SDK Base 2006 - Crashing when creating server in any multiplayer mod (215)
Issue transferred from https://github.com/ValveSoftware/Proton/issues/493.
@Cerega1827 posted on 2018-08-25T08:11:02:

When running through a normal Wine there is no problem