I'm a long time AMD user both my GPU and CPU. I have a powerful enough PSU and a b550m-plus mobo.
I'm looking to do gaming, light AI work, computer programming, running Docker server services.
I have a Radeon 6900xt, but it doesn't work well with Linux anymore. amdgpu fails to load, and I can only boot by adding nomodeset to my boot entry.
With ArchInstall I even tried reformatting with xfs, ext4, btrfs, without encryption, with and without LVM, selecting both ATI OS drivers for all GPUs, and drivers for AMD gpus, with systemd-boot and grub.
Even Fedora on USB only boots with nomodeset.
Windows seems to boot fine.
I assume it may be a problem with system reading the drivers from the GPU.
I have onboard HDMI for graphics, but I've never got it working.
tbh, my 6900XT was too powerful anyways. I do game in 4K with my 55" TV on the highest settings, but it seems I was still barely using the GPUs full potential.
Funny enough, I seem to have had more problems with high end GPUs in the past than low end GPUs.
(i am an arch user as well, but i mean this comment in good spirit, i am not tryinng to be sarcastic or downplaying)
have you tried bazzite/ublue or other "ready to use" immutable distros? In theory, 6900xt should work flawlessly with the open drivers that come with most distros. I do not think you have to buy anything. If you really want to buy, maybe 9070 (or 9060)(has that been released or not), but that would still be an upgrrade, and you seemingly want a downgrade.
file systems ideally should not matter at all for gpus. neither should encryption
on arch, I do not think you have to do anything for arch drivers. you just need base linux package, and linux-firmware (default is all firmwares, but if you do not want want that, you just need linux-firmware-amdgpu). other than that, just vulkan-radeon for vulan, and that is about it. ypu may install something for monitoring power usage, maybe finnd something to under/overvolt, but that is it, there should not be anything required for setup.
Funny enough, but sadly, Windows was the only one that booted normally.
that is indeed sad