I bought a not too expensive TCL qm6k with game master mode. Whenever it detects Xbox series S input, it turns on the mode by default. On menu it stays at 1440p but when I start a game, it switches to 4k 120hz- and the input lag becomes horrible!

Turns out it does not even care if I set lower resolution in Xbox display settings. So I had to just disable game master mode. And I don't miss anything.