After the update to Proton 11, as well as experimental, Serious Sam games(Fusion, 4 and Siberian Mayhem) all fail to utilize the SteamAPI which either load you as "Guest 1" or ask you for some login credentials. Reverting back to Proton 10.0-4 fixes the issue.
Hello again @kodatarule, please add PROTON_LOG=1 %command% to the game's launch options, reproduce the regression, and attach the generated $HOME/steam-$APPID.log to this issue report as a file. (Proton logs compress well if needed.)
Hello, here is the log for siberian mayhem, identical story to ss4(and also ss fusion too).
proton 10.0-4x1 2026-08proton experimentalx1 2022-01PROTON_LOG=1x1 2026-08
Compatibility Report
System Information
I confirm:
Symptoms
There is no audio, unless you manually switch to OpenAL in the game's settings. After that it's fine.
Don't think it needs a Proton Log file this time, as it's just an XAudio issue as by default it selects "XAudio2 2.9".
Reproduction
Just try the game and hear nothing until you swap the settings.