Today I tried updating the branch to b41multiplayer. When I launch the game on steam everything runs smoothly during startup (loading textures, animations etc.) until the text informing about "launching public servers" appears, when the game just closes instantly. The same happens in compatibility mode. When I return to b41singleplayer everything is back to normal.
My operating system is Ubuntu 18.04.5 64-bit. I tried checking the integrity of the files and it is correct.
console.txt
10-12-21_14-35-15_DebugLog.txt
