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. 
@mwl @gnomon My personal feeling as a long time user of ZFS and also of ZFS on Linux specifically, is that root on ZFS is definitely "danger, experts only" territory today unless you can find a distribution where it's officially fully supported so it's tested, and maintained by them.
My personal view is that ext4 root + ZFS homedir+etc pool is the best and easiest way to go (and how I do it on my desktops). You lose some space, but it's much easier to deal with.
@mwl @gnomon For typical Linux scenarios I'm not sure ZFS root gets you very much (and it does get you pain and worry). ZFS integrity checking is somewhat redundant with good package managers being able to verify checksums for most everything (and then you can reinstall anything broken). But maybe there are people out there who've really used rollback after upgrades.
(Having flexible space usage would be nice, but ... modern disks have gotten big.)
@Tubsta @mwl @gnomon My personal view is that rollbacks are such a blunt hammer and so badly or not supported by software¹ that it would have to be something massive to get me to do a system-wide rollback instead of reverting a package back. And if I don't catch it right away, a rollback will also probably roll back other things I want to keep, and etc.
¹ eg Firefox explicitly doesn't guarantee that you can use a slightly older version of Firefox on a profile that's been touched by a newer one.
Michael W Lucas 
Chris Siebenmann
Jason Tubnor 🇦🇺