The way https://sources.debian.org/src/shim-signed/1.40/debian/shim-signed.postinst/ is written, I would also assume triggering grub installation would be enough. Would it be possible to change that code? I am also a systemd-boot user and would like to finally remove grub, as it introduces an unnecessary attack surface and wrongly overrides the boot order on upgrade. This bug seems the last item blocking the transition. Cheerio, Matteo