recover-grub.sh

sudo cryptsetup luksOpen /dev/nvme0n1p7 linux-root  # decrypt LUKS
sudo vgscan
sudo vgchange -ay
sudo lvdisplay
sudo mkdir /mnt/linux
sudo mount /dev/vglinux/root /mnt/linux  # yours might be named ubuntu-vg
sudo mount /dev/nvme0n1p2 /mnt/linux/boot  # in case you have a separate unencrypted /boot
sudo mount /dev/nvme0n1p1 /mnt/linux/boot/efi
sudo mount --bind /dev /mnt/linux/dev  # so the makeshift system would be aware of stuff
sudo mount --bind /proc /mnt/linux/proc
sudo mount --bind /sys /mnt/linux/sys
sudo mount --bind /run /mnt/linux/run
sudo chroot /mnt/linux  # enter what you have created
grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=ubuntu --no-nvram
update-grub