It appears Linux root-on-ZFS is a mess. No standard way to do it. Kernel updates require recompiling ZFS. Boot environments are a cornucopia of constantly evolving hacks.
If you're actually using #ZFS on root, on #Debian, what's your preferred hack to make that happen? #sysadmin
I suspect #openzfsmastery might need to assume root on extFS and data on ZFS, leaving root-on-ZFS for the advanced user or a terminal chapter. 
well, ⬆️ sparked discussion.
There are linuxes that integrate ZFS into the installer, like Alpine and Chimera, and support ZFS on root. Good for them!
In general, though, more most linuxes, ZFS on root is an edge case that requires above average expertise with the boot loader. (If you have that expertise you think it's not much, but for many folks it IS a big deal.) Properly covering ZFS on root on Linux would require I write a book on initrd, UEFI, and more. I don't want to write that book. The workarounds various folks use evolve constantly, and by the time the book comes out they would have changed.
Looks like Linux ZFS root with ZFSBootMenu will be relegated a final chapter for the advanced user. 
Michael W Lucas 
Jens
Michael Dexter