Is it possible to run macOS in a virtual machine on Linux? I have an slightly-aging iMac running the macOS Sierra (fully legal) and a subscription to Adobe Creative Cloud that I keep around just for handling incoming files and punting them into my usual Linux based workflow. Often this means pulling something apart that came from a designer in Illustrator and exporting the pieces to for use in an open source publishing workflow.

Unfortunately this computer has gone on the fritz and is giving me nothing but the Spinning Beach Ball of Death™. I've tried to no avail to figure out what ails it and am desperate to convert some AI stuff that came in to sane SVG's.

Is it possible to run a full-legal version of macOS inside a virtual machine on Linux? Have lots of RAM and plenty of horsepower, I just don't know where to start. I remember playing with some pirated images in VirtualBox back in the day and they ran like a mule on drugs—and were more ornery. I need something to actually get a couple hours of work down without it taking all week.

What's the best emulation system to use and what's the legal path to acquire a  machine image? Or is there another way to do this? Is there a cloud provider that I can VNC into and run my licensed software on? What tree should I be barking up?
Well... if we assume that by 'legally' you mean according to Apple's EULA [there's a lot of bickering about that, so to avoid complication that's the definition I'll use.

Apple's EULA states, in short, that you can only run an Apple OS on Apple hardware; anything else is 'illegal'
see, I had to use that term, didn't I? ;-)

So, of course you could run it in a VM in Linux, but only if your Linux machine was actually a Mac [which would be rather pointless].

They only alternative I'm aware of would be to use a cloud instance &amp; the only one of those I've really heard of [though never used] is MacinCloud
It was discussed on Stack Overflow a few years ago [2012] so that might be worth a look at.