I remember when I first learned about GNUstep in 2004 when I was in high school. It's a shame GNUstep never took off; we could have had an ecosystem of applications that could run on both macOS and Linux using native GUIs.

With that said, the dream is not dead. There's a project named Gershwin (https://github.com/gershwin-desktop/gershwin-desktop), which is a Mac-like desktop environment built on top of GNUstep. Gershwin appears to be heavily inspired by Apple Rhapsody (https://en.wikipedia.org/wiki/Rhapsody_(operating_system)) with some modern touches.

My graduation thesis was to port visualisation software from NeXT into Windows, obviously rewriting it in the process.

My supervisor used to have a Cube, and every time I visited his office for demos or questions, there it was left in the corner, with the expectation that everything related to NeXT was going to be away.

Thus this project, and others, as means to keep the research going.

This was before Jobs coming back to Apple, and OpenStep not really going as well as hoped for.