Your log shows: grub-install: error: /usr/local/lib/grub/x86_64-efi/modinfo.sh doesn't exist. Please specify --target or --directory.
So you have a version of grub installed under /usr/local that is not part of Ubuntu. This is not a bug in Ubuntu, but with your local overrides of grub which are wrong for your installed system. ** Changed in: shim-signed (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1749986 Title: package shim-signed 1.33.1~17.10.1+13-0ubuntu2 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/shim-signed/+bug/1749986/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs