I just built my second penta SATA hat ZFS system using a Rock Pi, this time with a Rock Pi 4c. I had to struggle a bit getting ZFS to build from source on my prior system that was running Armbian 20.08.9.
Now, under Armbian 21.02.3 Buster, no need to build manually from source, just use apt to install from their repository (it is still built from source, but dkms does the work for you):
`sudo apt -t buster-backports install zfs-dkms zfsutils-linux`
See also “zfs just works now on armbian: 2-step instructions”