Main things to note with OpenCore: All properties must be defined, there are no default OpenCore will fall back on so do not delete sections unless told explicitly so. If the guide doesn't mention the option, leave it at default. The Sample.plist cannot be used As-Is, you must configure it to your system;
Keep in mind that using KVM/QEMU on UnRAID still relies on using OpenCore or Clover (the predecessor of OpenCore) as the boot loader to attract the hardware for macOS so the same restrictions on Apple updates and such apply on KVM/QEMU that would apply on bare metal.
I use GRUB iowr.mod and outb commands to disable the AMD GPU on boot so it's not even seen by Linux. But when I boot macOS, at some point during the session something enables discrete graphics and I get a kernel panic. I also get a kernel panic when doing any kind of software update (it's now stuck on 10.13.6).