I made a strace for the installation process and find the following error in a subprocess, which seems to be the cause.
strace -qf -o /tmp/grub_installation.log dpkg --configure grub-efi- amd64-signed ** Attachment added: "Strace log extract for the dpkg --configure strace -qf -o /tmp/grub_installation.log dpkg --configure grub-efi-amd64-signed" https://bugs.launchpad.net/ubuntu/+source/grub2-signed/+bug/1753518/+attachment/5070906/+files/extrait_log_grub_error.txt -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1753518 Title: package grub-efi-amd64-signed 1.93+2.02-2ubuntu8 failed to install/upgrade: installed grub-efi-amd64-signed package post- installation script subprocess returned error exit status 1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2-signed/+bug/1753518/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs