Experimental code ready for testing to enable HDMI 2.1 FRL with AMDGPU on Linux
(www.gamingonlinux.com)
Possibly. If you have the option to use DisplayPort instead of HDMI, that should also resolve it today.
I think it also depends on what distro you're using. On Linux Mint Cinnamon, which still uses X11 by default, I haven't been able to use the highest refresh rate of my monitor. But the experimental Wayland support did it without issue.