reddit[.]com/r/ROGAlly/comments/1niwsfi/guide_for_enabling_the_full_screen_experience_on/
windowscentral[.]com/gaming/pc-gaming/the-xbox-app-will-now-show-and-run-all-your-games-from-steam-gog-and-more-on-windows-11-its-the-new-hub-for-pc-gaming
They've added to the Game settings in Win11 25H2, with a full screen Xbox app mode tailored for hand held rigs, including reduced background processes. At the same time, the Xbox app has been upgraded to work with every installed game, whether it uses the Steam, Epic, or some other launcher. You will Not see this after installing the 25H2 ISO for the Insider Release Preview build 26200 currently available. It *might* be available with the 27924 build ISO for the Canary channel -- those trying it out have done the full enrollment to the Insider program and gotten 3 or 4 updates since the ISO version was released. The Reddit post also shows the steps to turn the feature on using the Vive tool -- the Vive tool lets you turn on features that are present but unactivated.