I was about to say macOS uses a microkernel, but on checking it seems that it's hybrid. Also, the source isn't available, so might not be what you're looking for.
>Also, the source isn't available, so might not be what you're looking for.
It is available, and it's called darwin-xnu:
https://github.com/apple/darwin-xnu
a mix of Mach and a FreeBSD kernel:
https://i0.wp.com/www.linuxandubuntu.com/wp-content/uploads/...
And a really good yt presentation:
24C3: Inside the Mac OS X Kernel