Very bad news here, while i was thinking that the Xbox Series X/S would play an UWP game better than the Xbox One X do (where i finally was able to makes my both games to run at 60FPS on it), well it is not! It stutters every seconds!! That's a shame that the most powerfull console of the world can't handle a 2D game that the Xbox One X do.
So i was wondering, is it because they limited the perfs of the UWP games on Series X/S or there is something to improve in the game to makes it to work on Series X/S... Well actually i don't know what to do as i don't own a Series X/S and i don't know if it is possible to turn them in dev kits...
A video showing the issue: