I've just stumbled on DarkStar, a Xerox Star emulator.
The GUIs we use today are a direct evolution of the work done on Xerox PARC in the 70's, resulting in the Alto and other Xerox computers that pioneered GUI on consumer products until Steve Jobs dropped by the lab for a visit.
The Star (1981) was more polished than the Alto and is definitely worth checking out!
💾 emulator: https://github.com/livingcomputermuseum/Darkstar
The website has configuration info & links to software downloads.