grub-install

gistfile1.txt

# GRUB Chroot Repair

sudo mount /dev/mapper/debian--vg-root /mnt
sudo mount /dev/sdb2 /mnt/boot
sudo mount /dev/sdb1 /mnt/boot/efi

for i in /dev /proc /sys /run; do sudo mount --rbind $i /mnt$i; done

sudo mount --make-rslave /mnt/dev
     
sudo chroot /mnt /bin/bash
     
# not necessary
# mount -t efivarfs efivarfs /sys/firmware/efi/efivars

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=debian12 --recheck
update-grub
     
     
# umounts
exit
     
sudo umount -R /mnt
sudo reboot