Ubuntu ZFS install hangs before reaching grub menu

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After upgrading some packages and restarting, I can no longer reach the grub menu. My system hangs at the motherboard logo and provides no other output.

I can boot to an Ubuntu Installer USB, and I can even get my ZFS pool mounted, but I’m hesitant to try any kind of grub repair since it sounds like that works a bit differently in ZFS world. I wouldn’t be quite sure where to start.

As an alternative, I’ve attempted using these instructions ( to use the Installer’s grub to boot my ZFS system but it fails:

Begins Importing pool 'rpool' using defaults ... Failure 1

I suspect “force” is needed since I imported it in the USB recovery environment but I can’t find how to provide that flag in grub.

I’m at a loss and would very much prefer not to rebuild my system. Does anyone have any suggestions on either of my approaches?

I am running Ubuntu 21 or 22… if I could get further in the boot process I would know for sure. Grub version on the installer is 2.04.


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