Comment 11 for bug 2029260

To recover, I used this guide:

https://openzfs.github.io/openzfs-docs/Getting%20Started/Ubuntu/Ubuntu%2020.04%20Root%20on%20ZFS.html#rescuing-using-a-live-cd

for the step which goes "Do whatever you need to do to fix your system." I used:

Comment out 'set -u' for example:
vi /mnt/etc/grub.d/10_linux_zfs

update-grub
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found linux image: vmlinuz-6.3.0-7-generic in rpool/ROOT/ubuntu_jyphyz
Found initrd image: initrd.img-6.3.0-7-generic in rpool/ROOT/ubuntu_jyphyz
Found linux image: vmlinuz-6.2.0-23-generic in rpool/ROOT/ubuntu_jyphyz
Found initrd image: initrd.img-6.2.0-23-generic in rpool/ROOT/ubuntu_jyphyz
Found memtest86+x64 image: /BOOT/ubuntu_jyphyz@/memtest86+x64.bin
Warning: os-prober will not be executed to detect other bootable partitions.
Systems on them will not be added to the GRUB boot configuration.
Check GRUB_DISABLE_OS_PROBER documentation entry.
Adding boot menu entry for UEFI Firmware Settings ...
done