I’m curious about migrating an Ubuntu desktop machine from ext4 to ZFS now that it is supported at the installer level. Here is documentation and a nice write up from Phoronix - https://www.phoronix.com/news/OpenZFS-Ubuntu-24.04-LTS
Current setup is running Timeshift rsync snapshots to an external disk ext4.
Desktop Machine:
i5 Intel Nuc with 12gb ram and single 512gb SSD running Ubuntu 22.04
I think that’s a pretty nice option if you’re thoroughly “nested” into one specific desktop PC with a myriad of customizations, apps, and configurations that you built up over a long time with very little documentation and you’re scared of losing it.
Personally I went the other way–I mercilessly pared down my dependency on any configuration I couldn’t easily recreate. Data I care about goes on ZFS. Application stacks that are truly a massive pain in the ass to recreate go into VMs which are stored on ZFS. But even in the era of ZFSBootMenu and direct-install docs at OpenZFS like the one you listed, I still most frequently do an ext4 root, because it’s the absolute least hassle to put in place, and because I can literally replace my desktop environment in 15 minutes maximum.
If more than 50% of the disk is free it does a simple two-step move-to-end then copy back approach. If <50% is free then it does an fstransform-style slice-by-slice conversion, 64Mb at a time.
Works on boot drive or any other attached volume, and the final result is nearly identitcal to Ubuntu’s native ZFS-on-root setup, so it doesn’t cause any funkyness at the OS level.
If you like experimenting with Ubuntu interim releases (like 25.04, 25.10), you will discover that their do-release-upgrade feature will not work if you have the stock zfs package installed. I put this off so long now I have to do a full OS reinstall. For me, this is really inconvenient bc I have an amazing amount of changes to /etc and all my libvirtd data is in the OS default location. So it depends on where you want to spend your time.