If you could make a non-linux OS go mainstream, which one would you pick?
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
I feel like HURD is the generational starship of operating systems. Will never be completed in my lifetime but eventually my great great grand children may some day use it.