If its possible to compile & and sign iOS or MacOS apps that would be VERY useful in CI environments, but yeah hard to think of other killer command-line apps that only run on MacOS.
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.
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.
Right, it's meant for portable desktop apps. You have to compile iOS apps on a Mac anyway so I'm not sure there'd be any demand for Conveyor's cross-building support for iOS apps.
If you target cross-platform frameworks that don't require Apple's toolchain, it can be made to work. For instance if you write an Electron or JVM app for the desktop then Conveyor can ship it from anything, because all the native components come pre-compiled in that case. But I don't think many people are writing mobile apps in that way.
