I make the specification of non-linux because otherwise this would just become a thread full of obscure distros that do the same thing as a million other distros.
Some lesser known OSs:
- AROS - based on Amiga OS, has some derivatives like IcarOS and MorphOS
- Haiku - based on BeOS
- Redox - Unix-like, made in Rust (might technically count as linux?)
- Serenity - Unix-like, very late 90s look and feel
- Kolibri - Tiny OS, the image is ~44MB. It also has a smaller version that fits in a single floppy.
- PhantomOS - When 3 Russians decide to turn everything about a typical OS upside down.
I’d say so. It was built to be the sort of general purpose OS that Linux is, only taking into account everything we’ve learned about how to make a good operating system from the whole history of *nix. And Plan 9 is newer than Linux in the sense that its first release came out after the Linux kernel’s first release. X11 has even been run on Plan 9 with adapter layers.