Gamemode launching on wrong monitor

Desktop.
2 monitors.
Main monitor 4K 42", secondary 24" vertical setup. Bazzite always starts directly to game mode, on the wrong screen, at the wrong orientation. I've tried disabling the screen from settings, and desktop mode won't even detect it now. Starting game mode again, chooses the wrong monitor. Any tips? I've looked through settings, but couldn't find any obvious places, in OS settings or Steam.
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