In 1995, another PC operating system launched its first version around the same time as Windows 95 was released. It was called BeOS, and it tried to become an alternative to Windows and Mac.
I read somewhere that the project is really hurting due to the original programmers having little to no time to devote to it, so I'm not expecting to run it on a Raspberry Pi anytime soon.
That doesn't surprise me. I have Haiku running in a VM, but haven't looked at it in 2 years, despite the fact I used BeOS as a daily driver back in the day.