Although I think it would be very interesting if I were wrong :)
For example, Gnu Hurd and Mach microkernel systems run a microkernel. OS X is a Mach-derived system, in fact, IIRC. NeXTSTEP was a microkernel, also Mach-based. Minix 3 is largely microkernel in nature.
https://en.wikipedia.org/wiki/Category:Microkernel-based_ope...
(I ran QNX on a desktop for awhile, in fact, as well as more-normal ones.)