I have not tried this myself, but this is my propsed course of action:
- Try exporting the pool again, if it fails due to being in use, move the system dataset to the boot-pool (if possible) and try again. You do this in System Settings → Advanced → Storage.
- Try exporting again, if you can’t because it’s still in use, restart and try this step again.
- If step 2 worked, try importing using the GUI.
- If it fails try importing using
sudo zpool import -R /mnt personal, which has the proper altroot flag set.