4k Monitor 240hz won’t go above 120hz

Hello fellow Gnome users.

A few days ago, I received my new monitor from Samsung (Odyssey OLED G8 G80SD). However, I can’t get it to go above 120Hz at 4K. I’ve tried both the DP port and HDMI 2.1. But when I use Windows (Dual Boot), it works without any problem.

Is it also possible to set the resolution to 150% instead of 100-200-300%, as the display settings only let me choose from these options?

Is there a solution to this?

I also can’t get FreeSync Premium PRO to work, which I believe should work in Gnome.

As far as I know, Gnome doesn’t support HDR yet.

Edit: Ok. So Linux don’t support HDMI 2.1

Thankful for any help :)