Out of curiosity I went looking to see if there are any macOS compatibility layers for Linux these days.
Good: I found Darling, which handles the low-level translation and can run command-line programs compiled for Darwin, but doesn’t have much in the way of GUI support. (If I ever need to run the XCode CLI tools on a Linux box, though, this will be the way to do it.)
Bad: A tech article that looked like someone copy-pasted an article about Wine and replaced every instance of “Windows” with “MacOS.”
Ugly: Running macOS in a virtual machine. Good luck with that!
That’s about it, which is, frankly, more than I expected!
(Of course, most FOSS programs that run on macOS can be compiled for Linux anyway. When there’s no Linux version of a proprietary macOS app, there’s often a Windows version that can run under Wine. And when it’s macOS-specific, there’s usually something that will do the same job.)