"Legitimate" MacOS VM on Linux running on iMac?

Hey Hackintoshers,

I have an iMac 12,1 (Mid-2011 21.5" LCD w/ 2.5 Ghz i5) which is no longer supported past High Sierra. I'm updating the 8-year-old HDD with an SSD, and I'm going to put Linux (probably POP_OS!, an Ubuntu variant) on it.

The only thing I really need macOS for right now is iMessage, so I'd like to run a MacOS vm under virtualbox, or some other free VM platform.

I've seen the download links for pre-hacked, pre-installed MacOS VM images, but I have some serious trust issues with using a disk image I downloaded online.

Does anyone know where I can find instructions for installing a MacOS VM on a Mac running linux, or something similar? I don't want to use a pre-made macOS vm image.

I guess I'm thinking that the fact that I'm running Linux on actual Mac hardware might make the hacking process a little easier, but I have no rational reason for that to be -- running a VM abstracts an awful lot of stuff that might make a stock MacOS install feel "at home."

Thanks all!

P.S., I know it's supposed to be "Mac OS," not "MacOS." I'm in my forties, and I remember when it was called "MacOS (8 & 9)," and before that, System 7, and before that, System Software 6.0.4 (because 0.3 was buggy). (And before that, System File version this and Finder version that.)

Now get off my lawn ;)

Author: @NerdOfManyTrades