[TUHS] Is there a good, even definitive, list of reimplementations of the Unix kernel? What would good cut-off criteria be?

[Andy Kosela via TUHS]

What about Coherent? Looks to me like a clean reimplementation of UNIX. It
was quite popular on x86 in the 80s. I liked its minimalistic approach
compared to other UNIX clones at the time.

--Andy