Comment by BSDobelix

>but it’s a vastly different kernel (derived from the Mach microkernel).

XNU is a combination of a FreeBSD-Kernel (Networking, Filesystem, etc) and a Mach-Kernel (scheduling, ipc, virtual-memory etc):

https://en.wikipedia.org/wiki/XNU

https://www.youtube.com/watch?v=-7GMHB3Plc8