Troubleshooting a second monitor turned into AMD driver issues


I have a Radeon 6900 XT in my build and initially, all I wanted to do was run Qubes across two monitors. Both monitors work and are of identical models. I can boot with either but not both: whichever screen displays my POST will display my OS from that point forward.

I have already re-imaged to stock Qubes. I tested this on both KDE and Xfce.

  1. I have these flags in my default grub config: nomodeset=0 rhgb quiet. Removing the modeset flag but not the other two will finally show both monitors when booting but disable my keyboard at LUKS decryption and I have to restart. Removing all three will get past LUKS decryption but ultimately hang waiting for processes to launch. At this point, I cannot even launch a shell.
  2. My kernel is completely up to date and is on kernel-latest. modprobe amd will return nothing but modprobe amdgpu will return "unable to insert “amdgpu”: invalid argument. In contrast, modinfo amdgpu returns a full list of firmware and shows a location of /lib/modules/6.2.10-1.qubes.fc32.x86_64/kernel/drivers/gpu/amd/amdgpu/amdgpu.ko which aligns correctly to my kernel version.
  3. I also tried installing the RPM package directly from AMD for my GPU but it says qubes is an unsupported OS, was not surprised at this one.
  4. Display tools on either KDE or Xfce do not see the second monitor. Xrandr returns an error failed to get size of gamma for output default in dom0 but from the looks of other threads, it’s because dom0 isn’t intended to use GPU drivers in the first place. Cool. sudo glxinfo - B shows my monitor as device name llvmpipe with a vendor of Mesa/ Looks like more evidence that dom0 should be off CPU and not GPU. Cool, I still want to figure out why I can’t use two monitors and every thread I’ve read points to GPU drivers as the culprit.

I am genuinely lost here, I just want to work off both monitors instead of only one. Any help would be greatly appreciated.

It’s not enough saying which GPU you have. You have to thoroughly describe your hardware, and the steps you are taking to use both monitors.
For example, I have a laptop and have Nvidia dGPU, so if I want to use more than one monitor, I have to enable discrete in BIOS, because HDMI/DP are tied directly to mainboard. Except