dpkg --configure -a resulted in dpkg: error: dpkg frontend lock is locked by another process, so I restarted the machine after all and updating worked fine.
Before that I killed the dpkg process and tried to run it, which resulted in that:dpkg --configure -a Setting up grub-efi-amd64-signed (1.173.2~20.04.1+2.04-1ubuntu47.4) ... debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable dpkg: error processing package grub-efi-amd64-signed (--configure): installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 1 dpkg: dependency problems prevent processing triggers for shim-signed: shim-signed depends on grub-efi-amd64-signed | grub-efi-arm64-signed; however: Package grub-efi-amd64-signed is not configured yet. Package grub-efi-arm64-signed is not installed. dpkg: error processing package shim-signed (--configure): dependency problems - leaving triggers unprocessed Errors were encountered while processing: grub-efi-amd64-signed shim-signed
Either way, solved not in the most elegant way, but solved 😄