Reinstall grub menu with UEFI, lvm, and separate boot partition

reinstall-grub.sh

#!/use/bin/env bash
# burn Ubuntu Live CD nearest to the installed system
# undock, connect network cable, Live CD, and boot off it
# sudo -i
set -e
apt update
apt install lvm2 # this is already installed in Ubuntu 23.10 Live CD
fdisk -l
lvscan
mount /dev/vg0/lv-0 /mnt
cd /mnt
mount /dev/nvme0n1p5 boot # or nvme2n1p5 if using dock
mount /dev/nvme0n1p1 boot/efi # or nvme2n1p1 if using dock
for i in /dev /dev/pts /proc /sys /sys/firmware/efi/efivars /run; do mount -B $i /mnt$i; done
cp /etc/resolv.conf etc
chroot .
# unneeded: apt update
# unneeded: apt install linux-modules-6.5.0-9-generic linux-modules-extra-6.5.0-9-generic 
# unneeded: modprobe efivarsfs # always fails
apt install --reinstall grub-efi
grub-install /dev/nvme0n1 # or nvme2n1 if using dock
# uneeded: grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=ubuntu --recheck --no-floppy /dev/nvme0n1
update-grub
exit # chroot env
# reboot
# after reboot:
# sudo -i
# echo GRUB_DISABLE_OS_PROBER=false >> /etc/default/grub
# apt install os-prober
# os-prober
# grub-install # needed?
# update-grub
# reboot

https://wiki.debian.org/GrubEFIReinstall may have the answers