I dug out a
Gigabyte X99 Ultra Gaming motherboard together with an i7 6850K and attempted to get MacOS running on it. I had experience with Sierra and High Sierra on a
Gigabyte X99-UD4 / i7 5820K combo before and still kept the EFI folders from that time. Using them I had no problems getting preinstalled Sierra and High Sierra partitions to boot up on the new system. Also tried with a preinstalled Mojave installation on a SATA SSD and had little problem getting it to boot using the same performance patches from High Sierra config.plist.
So, onto Catalina. I did not try to install Catalina on the system but just used a preinstalled Catalina 10.15.7 on a SATA SSD to try to boot.
Initially I tried to copy the performance patches from the High Sierra / Mojave installations but Catalina 10.15.7 just refused to boot, hanging at the Apple logo, no matter how many times I tried. I did use the boot argument npci=0x2000 and FakeCPUID 0x0306F2 but still no dice.
So, I decided to start from the beginning and used the original EFI folder generated from Unibeast 10.3.0 and started from there.
Used the boot argument npci=0x2000 and FakeCPUID 0x0306F2, changed the SMBIOS to MacPro6,1, and success! Catalina booted up, no "performance patches" were necessary.
I was a little surprised but delighted that actually just a little modification from the original Unibeast EFI enabled Catalina 10.15.7 to boot up. The included IntelMausi kext enabled the Intel LAN on the motherboard (I deleted the Atheros kext as I don't need the second LAN port.) and the addition of AppleALC 1.5.0 enabled motherboard audio.
So the test is a success. As I don't use this system as my main system I will stop here. Knowing that Sierra / High Sierra / Mojave / Catalina all work well on this system, I can turn to this system or my Z370 system if my main Z390 system has a problem in the future.