If they had good GUI support then some more things open up but nothing really essential. Garage Band has no equal in terms of ease of use, if you are into that sort of thing.
The Firefox source tree has every tool available for cross-compilation from Linux → macOS, which is how Firefox is built for macOS.
It has built in support for Electron, JVM, Flutter and even native apps (although of course then you still have to compile the native binaries on macOS yourself).
That also works the other way around. You can ship to Windows from Linux or macOS.
Well, not if somebody finds a way to run the compilation elsewhere!
Hence my comment!
Right now, iOS dev requires to own a recent Mac machine, which is hell of expensive, and moreover needs to be renewed every few years...
Completely unjustifiable...