Comment 1 for bug 1687664

FWIW: Found another case, where grub2 fails:

May 3 15:37:28 in-target: grub-common is already the newest version (2.02~beta2-36ubuntu3.9).
May 3 15:37:28 in-target: 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
May 3 15:37:28 main-menu[422]: (process:4764): grub-probe: error: failed to get canonical path of `rpool/ROOT/linux'.
May 3 15:37:28 main-menu[422]: (process:4764): grub-probe: error: failed to get canonical path of `rpool/ROOT/linux'.
May 3 15:37:28 main-menu[422]: WARNING **: Configuring 'grub-installer' failed with error code 1
May 3 15:37:28 main-menu[422]: WARNING **: Menu item 'grub-installer' failed.
May 3 15:37:40 main-menu[422]: INFO: Falling back to the package description for brltty-udeb
^C

~ # zfs list
NAME USED AVAIL REFER MOUNTPOINT
rpool 163G 760G 19K none
rpool/ROOT 2.55G 760G 19K none
rpool/ROOT/linux 2.55G 760G 1.61G /target
rpool/ROOT/linux/home 19K 760G 19K legacy
rpool/ROOT/linux/var 963M 760G 963M legacy
rpool/VARSHARE 19K 760G 19K /target/var/share
rpool/dump 64.0G 824G 8K -
rpool/swap 96.0G 856G 8K -

~ # zpool status
  pool: rpool
 state: ONLINE
  scan: none requested
config:

 NAME STATE READ WRITE CKSUM
 rpool ONLINE 0 0 0
   nvme0n1p2 ONLINE 0 0 0

~ # zpool status -P
  pool: rpool
 state: ONLINE
  scan: none requested
config:

 NAME STATE READ WRITE CKSUM
 rpool ONLINE 0 0 0
   /dev/nvme0n1p2 ONLINE 0 0 0