Yeah, let's gloss over the eGPU issue with the Mac Mini.
There's been some drivers issues with AMD mentioned extensively, mainly to do with undercooked ones for RDNA, but also seemingly affecting the older Polaris ones.
Obviously you'd expect these to be ironed out soon but it's another issue to add to the list. My impression is that the number of users demanding a headless Mac they can add graphics card is too small to be worth addressing by Apple with a box that will allow internal upgrades like PC desktop users are used to. A headless MacBook Pro 16" anyone?
Far easier to put all this into a nice iMac case and put a nice screen on it.