Microsoft officially endorses Windows 11 on Parallels.

[KingOfPain]

Instead of being a straightforward port of x86 OS/2, PPC OS/2 was actually the only released version of IBM's grand unified operating system project, Workplace OS. This was a system design in which the core OS was a Mach-derived microkernel. Compatibility with user apps would be provided in the form of "personality" modules running on top of the microkernel - one for OS/2, another for Windows, etc. In theory, you'd be able to run multiple personalities side by side.

Sounds like an interesting concept, but I can see why development was quite expensive. And having to keep the compatibility of several personalities up to par would have been a monumental task.