The graphics are broken when connecting the Series X to a 1440p monitor

I just got a new 1440p/144Hz monitor and decided to stress test it with my Series X. The monitor is working flawlessly, but when I fired up Infinite’s campaign… The horror.

In performance mode the resolution was very low. Noticeably lower than when connected to my 55" 4k/120Hz OLED TV. Lots of detail were missing, tree’s leaves and branches so thin that merged with the sky, vegetation reduced to pixels, the mountains displayed pixels big as fists.

The Series X output is set to 1440p / 120Hz and VRR, if it helps.