CPU
Some games benefit a lot from the large L3 cache in the X3D cpus, f.e. the AMD Ryzen 7 7800X3D. Check whether it is true for the ones you play.
GPU
I’m running an AMD 6650XT GPU in Linux without any trouble, I even use vfio to use it in a Fedora VM without errors.
RAM
Buying 2x32GB gives you enough RAM to run a bunch of VMs while gaming. 2x16GB is more than enough for a gaming rig.
Priority one for me is that the motherboard allows for BIOS Firmware updates from a USB drive without having to boot an operating system. The user manual is usually the fastest way to verify that one.
Then I would look at PCIe slots, if I bought a new motherboard today I would want to have at least one PCIe 5.0 x16 slot and one PCIe 5.0 m.2 slot.
Oh, and searching the net for people having trouble with the motherboards networking or bluetooth when running linux distros is always a good idea.