I found the reason for this problem: it turned out to be the BIOS setting "Boot Order Lock". After disabling it, I saw the above message one more time, then Ubuntu started properly (and a new boot entry called "ubuntu" appeared in the BIOS).
I don't know if this is possible, but it would be a good idea to detect that the "ubuntu" boot entry wasn't actually created and display an error message. If it's not possible, an additional hint about "Boot Order Lock" or similar BIOS settings might be helpful (as well as showing the message for more than a split-second). ** Package changed: ubiquity (Ubuntu) => grub2 (Ubuntu) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1761895 Title: Post-install boot loop: "System BootOrder not found." To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1761895/+subscriptions -- ubuntu-bugs mailing list email@example.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs