I finally ended up rebooting and there was no problem (the efibootmgr entries were good).
The message after running apt-get upgrade : Paramétrage de grub-efi-amd64-signed (1.93.16+2.02-2ubuntu8.15) ... Installation pour la plate-forme x86_64-efi. Installation terminée, sans erreur Translation: Setting up grub-efi-amd64-signed (1.93.16+2.02-2ubuntu8.15) ... Installation for the x86_64-efi platform. Installation complete, no errors. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1869558 Title: After the update of "grub-efi-amd64-signed 1.93.16+2.02-2ubuntu8.15" ubuntu doesn't boot (Block device required error) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2-signed/+bug/1869558/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
