Comment 13 for bug 2041739

That would seem to indicate the Ubuntu Mantic installation process is creating the bpool with zfs flags that are incompatible with grub. I wonder if the problem is still present in Noble Numbat/24.04?

Are you able to check which zfs flags/features are set after the bpool is created? (use `zpool get all bpool` to get flags)

You will need to backup your /boot directory and recreate you bpool with the `-o compatibility=grub2,ubuntu-22.04 \` option, as described earlier in this thread.