I totally forgot to post here about what happened with Ryzen PCIe ACS (Access Control Services) support, for better IOMMU Groups granularity for PCI Passthrough.
According to
this, AMD told to a VFIO developer that Ryzen does support ACS and that it should be a Firmware option, supposedly found in a submenu called "NBIO Debug Options". However, that was nearly one month ago, and google results from that menu name pretty much only include that link, or other places where it was directly quoted. Does such menu exist in any reference Firmware, or any other place? What other options are missing?
Also worth mentioning, AsRock has been implementing SR-IOV support in some of their Motherboards. I think I never hear before of it being supported in a consumer Motherboard. So far, it is rather useless on its own as SR-IOV is only used by some NICs and the very latest AMD FirePros for GPU Virtualization, but they have limited Hypervisor support (I think only VMWare products, the amdgpu-pro Linux Driver still can't create Virtual Functions).
I don't know if it was mentioned elsewhere, but chances are it was since is rather major: A reviewer tested
Ryzen ECC support. It does work but is "incomplete", but I don't know how "incomplete" it is because is not that I see people doing such type of tests, nor know how a proper Server system with ECC would behave. Still, is has some potential...