I was able to successfully boot with upstream kernel version: 5.10.0-051000rc3-generic
This kernel package notably does not include the ZFS kernel modules (and those kernel modules did not build when I installed zfs-dkms). So it does seem possible that the bug I'm encountering relates to ubuntu kernel 5.8 and the various ZFS related kernel modules.
I was able to successfully boot with upstream kernel version: 5.10.0- 051000rc3- generic
This kernel package notably does not include the ZFS kernel modules (and those kernel modules did not build when I installed zfs-dkms). So it does seem possible that the bug I'm encountering relates to ubuntu kernel 5.8 and the various ZFS related kernel modules.