Im on good way to make on Z390 working
WinXP, Win7,Win10 + Linux (5 distro should be enough for every one) + Mac OS.. and i hope that Windows 98 at least within KVM (i have not PCI slot and so on physical it would be possible only with USB audio or which some lousy PCI-E to PCI adapter and even that it would be only for Win98, without Dos sound).
But Sata + USB controllers compatibility is really nightmare to make them working with all OSes, there is always something.. whole problem is mainly because of Windows XP (most problematic platform). Intel USB3 has no official drivers, only community one - which is working just for keyboard and mass storage, 3rd party USB3 controllers drivers never were too good espcialy with WinXP, but i had issues with Win10 with them too - maybe with exception Asmedia - i have 1 on the way.
Now i suffer with VIA USB3 , NEC was worse - in XP, main devices are working, but some secondary like Xbox 360 controller, Bluetooth etc are not - maybe because there is also some USB hub in the way, VIA is not also working during MacOS setup and im not sure if there is some MacOS driver for it, i know that Asmedia has one. I want to reach the state, when i will not have to reconnect anything based on selected OS, just select right bios profile (right main GPU) and maybe monitor input - if HDMI autoswitching will not working.
Sata controllers problem too, are fine with Windows - i had Marvel, but it has problem with Linux - at least with Solus Linux it needs special boot parameters, otherwise boot is very slow - minutes and it doesnt see my discs. Now i enable KVM with Mint through intel_iommu=on kernel parameter and met same problem, so i used Asmedia Sata - which booting slowly too, but it least after that see connected devices.
Only real reason for use additional Sata controller is actually to make GPT disks readable within Windows XP, which is not working with Intel controller + Paragon GPT driver - i reported it ~5 years ago and they never fix it.
Im now messing with NVME with my old XP install, with clean its working.. but i can live without it, after that i have 2 main things to go - make Mac OS working with Z390, i hope that with older install and Linux KVM.. after that i will 2 GPus for Win98 and WinXP and all would be great - i hope.
Im old goal oriented goatman, i care about facts and freedom, not about egos+prejudices. Hoarding=sickness. If you want respect, gain it by your behavior. I hate stupid SW limits, SW=virtual world, everything should be possible if you have enough raw HW.