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.
Serenity for sure. I love the 90s aesthetic and would like to see it make a comeback. At the very least I’d like to see their Ladybird browser become mainstream - we really need more alternatives to the Chromium family.