This experimental guide has been made official at [[Debian Buster Root on ZFS]].
If you have an existing system installed from the experimental guide, adjust your sources:
vi /etc/apt/sources.list.d/buster-backports.list
deb http://deb.debian.org/debian buster-backports main contrib
deb-src http://deb.debian.org/debian buster-backports main contrib
vi /etc/apt/preferences.d/90_zfs
Package: libnvpair1linux libuutil1linux libzfs2linux libzpool2linux zfs-dkms zfs-initramfs zfs-test zfsutils-linux zfs-zed
Pin: release n=buster-backports
Pin-Priority: 990
This will allow you to upgrade from the locally-built packages to the official buster-backports packages.
You should set a root password before upgrading:
passwd
Apply updates:
apt update
apt dist-upgrade
Reboot:
reboot
If the bpool fails to import, then enter the rescue shell (which requires a root password) and run:
zpool import -f bpool
zpool export bpool
reboot