To be honest, the only problems on this iMac are audio (fair to say Apple's fault), the screen only running at 4K max (Apple custom stuff involved for 5K, but hey, not complaining about 4K, go find me an AiO PC with a 5K screem), the amdgpu issue (not really an Apple problem, it's just a rarer chip and probably a dumb bugfix and the older radeon driver works fine), and the Ethernet and SD card reader being problematic (that's a Broadcom chip and their silicon is universally buggy; not Apple's fault, these chips have issues on PCs too)
So really just audio is the one thing that jumps out as broken and specific to this being a Mac. I personally happen not to care as I use an external audio interface anyway :-)
Actual installation is trivial, it's just standard UEFI pretty much. As long as the right GPU driver loads you're fine. Thunderbolt and all that works out of the box.