On 30 Nov 2020, OpenZFS version 2.0 has been released with plenty of new features and performance improvements: https://github.com/openzfs/zfs/releases/tag/zfs-2.0.0
Ubuntu Linux 20.04 LTS normally comes with kernel 5.4, with built-in ZFS version 0.8.3 (released Jan 23, 2020). Of course that's stable, but also quite old already.
Ubuntu also provides more recent kernel versions by using their HWE (linux-generic-hwe-20.04) and HWE Edge (linux-generic-hwe-20.04-edge) packages. For better support of modern hardware, you should use those kernel versions. Latest version so far was 5.8, but still with ZFS 0.8.4 (released May 12, 2020).
On 18 Jun 2021, linux-generic-hwe-20.04-edge has been updated to kernel 5.11 (5.11.0.22.23~20.04.6), which includes ZFS 2.0.2-1ubuntu5 kernel modules. Not the latest 2.x release to date, but that will surely come soon.
Now the only problem is that the ZFS tools included in package zfsutils-linux are still on version 0.8.3-1ubuntu12.9. So even if a newer kernel module version is installed, new functionality is not fully accessible.
Fortunately, Jonathon F provides newer ZFS packages in this PPA: https://launchpad.net/~jonathonf/+archive/ubuntu/zfs?field.series_filter=focal
After adding the PPA, the newer ZFS tools (2.0.4, released Mar 9, 2021) can be installed via apt update && apt upgrade. Nice.