OpenZFS on OS X

My Mac always hangs on shutdown when there are no pools connected: The screen gets black, the mouse pointer is still there and movable, but nothing else happens, even after hours of waiting. I assume a kernel panic is what happened.

I have known this problem for some years now: Can anyone produce it?

I solved this problem by setting up a dummy USB thumb drive as ZFS pool with no data on it that always stays in one of my USB ports. This does the trick.

I don't have this problem with 1.9.4 and macOS 10.14.6 (18G4032)

You could try booting with "-v" (I think you can hold cmd-v) to get a verbose boot.. this verbose output comeback at the reboot time, and you might see some message about it waiting for something...