Partly out of curiosity than anything, I wonder if this would work? I have a 17" MacBook Pro, and the latest version of macOS that it supports is 10.13, High Sierra. It would be interesting to try installing Catalina (10.15) as a guest on Parallels Desktop. I don't think it would violate Apple's terms of service (Catalina would be running on Apple hardware, although on top of a VM), but would Parallels Desktop provide the necessary hooks that Catalina needs? I may download a trial version to give it a try.