I had the exact same problem. In Lutris in the configure menu of the game, I was able to go to system options and add a new environment variable 'PROTON_DISABLE_LSTEAMCLIENT' and set the value to 1. Also under runner options add dll override 'winmm' and set the value to 'n,b'. After that it started no problem.
Found this on the cs.rin.ru page for this game from november 2025, might be worth a shot