AMD GPUs are cursed for me
Each time I try AMD graphics, something is fucked for me. Back with fglrx, fglrx just sucked, so I used Nvidia. Then I had an AMD right around when they finally had opensource drivers, but it was still buggy as hell. So I went with Nvidia again (first a GTX 790, then a GTX 1060). In the meantime I had a new work notebook where I also went with an AMD APU, and had driver crashes for a long time when I was in video calls and it had to decode multiple streams. That thankfully stabilized with Linux 6.4.
Since sooo many people in the community swear by AMD, I thought "dammit, let's try it again for my new desktop" and got an 7800rx ... and I have to reboot ~5 times until I finally make it to a running xserver or wayland session. Apparently I am hit by this problem (at least I hope so). But that doesn't even read nice ... the fix seems to be to revert another fix for powermanagement. So I either have a mostly non-booting card or suboptimal power management.
I start to regret having chosen AMD .... again :-/ I seem to be cursed.
I couldn't get my 6900XT to drive my G9 at 240Hz, but 120 isn't too bad. I should probably try again soon.
Been 20+yrs of some random flavor of driver problems for me, since my 9700 Pro at the very least.
Over DisplayPort? That's interesting, I knew AMD can't do HDMI 2.0 but there shouldn't be a problem with DP.
Might wanna try a proper new certified DP 2.1 cable, just to be safe.
I "only" drive a AW3423DW but no issues at 3440x1440 with 165Hz.
Indeed over DP. It works fine at 240Hz in Windows, but of course the graphics quality in games is not as good as with nvidia.
Anything interesting going on in the kernel log while connection doesn't work?
If so, you could maybe write a bug report at the amdgpu repo.
One thing I could imagine that is happening is that Linux chooses a higher chroma subsampling than on Windows. Had that issue before with a monitor that had a wrong EDID. Unfortunately it's a real pain to set the chroma subsampling on Linux with AMD.