I wonder if OpenCore would enable me to (a) passthrough an i915 GPU but not an AMD GPU; (b) run Catalina on a Mac that doesn't support it? I have an ancient macbookpro 8,2 with the defect that eventually leads to AMD GPU failure (it failed, was replaced under warranty extension, failed again same number of years later). I use GRUB iowr.mod and outb commands to disable the AMD GPU on boot so it's not even seen by Linu…
That's going to be a lot easier then OpenCore.