systemd-boot guidelines missing

I am trying linux-surface with Pop!_OS 22.04 on a Surface Pro 6.
By default it uses systemd-boot instead of GRUB (I am not seeking dual boot with Windows).

After running:
`sudo apt install linux-surface-secureboot-mok`
the installation guideline suggests:
`sudo update-grub`
which does not work for me and I am not able to enroll the key.