I was just bitten by the opposite problem:
- Ubuntu 20.04 VM, kernel 5.4.0, zfs 0.8.3
- running lxd snap, following “stable”
- lxd updated itself to 5.21
- Canonical muppets have removed zfs-0.8 tools from the snap
root@db:/home/brian# ls /snap/lxd/27049
bin commands criu etc lib lxc lxcfs meta share snap usr wrappers zfs-0.8 zfs-2.0 zfs-2.1 zfs-2.2
root@db:/home/brian# ls /snap/lxd/28155
bin commands criu etc lib lxc lxcfs meta share snap wrappers zfs-2.1 zfs-2.2
All hell has broken lose. Roll back the snap then?
snap refresh lxd --channel=5.20/stable
No: the muppets have also ensured that a rollback is impossible.
# systemctl stop snap.lxd.daemon.unix.socket
# lxd --debug --group lxd
...
time="2024-04-13T08:38:42Z" level=info msg="Daemon stopped"
Error: Failed to initialize global database: failed to ensure schema: schema version '73' is more recent than expected '69'
It seems going back to 5.21 plus HWE kernel upgrade is the only option - followed by migration to incus.
And I’m never touching a system with snapd again, except to remove it.
EDIT: It looks like they realised their mistake and released 5.21.1 with zfs-0.8 support: LXD 5.21.1 LTS has been released - News - Ubuntu Community Hub
(and turned 5.21 into an LTS release)