Right now the X11 backend sets _NET_WM_BYPASS_COMPOSITOR regardless of whether the window is fullscreen or not. On KDE this disables the compositor for the entire desktop which causes flickering whenever a windowed SDL application is started.
Can a hint be added to disable this behaviour? Changing the property once it’s been set or even calling XDeleteProperty has no effect.
Edit: Submitted patch to bugzilla - https://bugzilla.libsdl.org/show_bug.cgi?id=4085