It would be fair to say it's "quite simple" to port macOS apps to Linux if macOS apps were written against the Unix/POSIX API, but they are generally written using Apple's macOS-specific proprietary frameworks, meaning a Linux port of a GUI application would really be a re-write.
Adobe products look the same across Windows and macOS. I don't think they are using so much native stuff. They even ported their software to ARM, I think they could manage a Linux transition
Which is close to trivial if you're mainly using macOS APIs.
Of course Adobe probably has a lot of platform-agnostic stuff but which wasn't that straightforward to port but I'm pretty sure the UI and system stuff is still mainly using Cocoa.
I'm not even sure the macOS version would be necessarily that easier to port than the Windows one (then again there is probably not that much .net code in their tools)
"Quite simple" is an enormous overstatement here. The API surface of macOS is a vast superset of POSIX, including lots of libraries (AppKit, e.g.) that are not open-source.