Ok, a key point here is that your dbx includes Microsoft's recent revocations of older grub versions; and an examination of the daily image shows that it's currently using an old grub signed with the old key instead of the current grub:
$ sudo kpartx -a ~/devel/iso/groovy-desktop-amd64.iso $ sudo mount /dev/mapper/loop8p2 /mnt $ sbattach -d /tmp/grub.sig /mnt/efi/boot/grubx64.efi $ openssl pkcs7 -noout -inform DER -in /tmp/grub.sig -print_certs subject=C = GB, ST = Isle of Man, O = Canonical Ltd., OU = Secure Boot, CN = Canonical Ltd. Secure Boot Signing issuer=C = GB, ST = Isle of Man, L = Douglas, O = Canonical Ltd., CN = Canonical Ltd. Master Certificate Authority $ sudo umount /mnt $ sudo kpartx -d ~/devel/iso/groovy-desktop-amd64.iso $ This is not a bug in grub but in the construction of the daily images, which apparently do not automatically track the current grub. ** Package changed: grub2 (Ubuntu) => cd-boot-images-amd64 (Ubuntu) ** Changed in: cd-boot-images-amd64 (Ubuntu) Status: Incomplete => Triaged ** Changed in: cd-boot-images-amd64 (Ubuntu) Status: Triaged => Fix Committed ** Changed in: cd-boot-images-amd64 (Ubuntu) Importance: Undecided => High ** Changed in: cd-boot-images-amd64 (Ubuntu) Assignee: (unassigned) => Steve Langasek (vorlon) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1892754 Title: Unable to boot in UEFI+secure boot mode To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/cd-boot-images-amd64/+bug/1892754/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs