It is in the Ubuntu 19.10, Canonical its Ubiquity desktop installation program adds ZFS root file system installation options. Ubuntu 20.04 Desktop installer's had this simple installation options, but has now been hidden "advanced features (advanced features)" window (see below :).
Ubiquity in the "advanced features" area, may be mounted to ZFS root file system. This option is still considered experimental, but it is still the default EXT4 file system. By default, the option to select ZFS on Linux will install its Zsys daemon.
After using ZFS with the Ubuntu ISO 20.04 daily build and restart the system, when performing any APT transaction, there will be a new "saving system state (system state is saved)" message (see below). If the package upgrade / install / remove problems, run APT will trigger Zsys shooting ZFS snapshot.
By GRUB, the boot loader in more than a "history (history)" menu, see below.
From the History menu, you can select an earlier snapshot to boot. See below
