This generally indicates that GRUB's core image and modules are out of sync. That's more usual on BIOS installations, but it's possible on UEFI too. Perhaps you didn't have your EFI System Partition properly mounted on /boot/efi when upgrading grub-efi-amd64?
** Changed in: grub2 (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1098952 Title: grub_efi_secure_boot symbol not found after update to grub 1.99-21ubuntu3.7 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1098952/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs