Hello @Alejandro9509, we're using one issue report per unofficially supported game title, so I've gone ahead and transferred this issue report to https://github.com/ValveSoftware/Proton/issues/8205#issuecomment-4472811471.
proton experimentalx1 2026-05
Compatibility Report
System Information
I confirm:
Symptoms
Hi, I'm currently having a problem where, using Proton version 10 or Experimental, the game starts in borderless window mode. With Proton version 9 it works without issue. I'm currently using Fedora with GNOME; I believe the problem doesn't occur in KDE, but I haven't verified it.