I have Samsung QE65QN91AATXXH so 65" version of QN91A.
I have Xbox Series X connected to TV using included HDMI 2.1 cable.
I have Xbox set to 4K 120FPS.
I can't enable VRR (variable refresh rate) on Xbox. The option is grayed out. It doesn't matter if I use game mode on TV or not.
TV's and Xbox's firmware is the newest (I updated the TV on 13th Nov 2022).