lubuntu@lubuntu:~$ sudo apt install grub-efi-amd64-signed
Reading package lists... Done
Building dependency tree       
Reading state information... Done
grub-efi-amd64-signed is already the newest version (1.74+2.02~beta2-36ubuntu11).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
2 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] 
debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable
Setting up grub-efi-amd64 (2.02~beta2-36ubuntu11) ...
debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable
dpkg: error processing package grub-efi-amd64 (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of grub-efi-amd64-signed:
 grub-efi-amd64-signed depends on grub-efi-amd64 (= 2.02~beta2-36ubuntu11); however:
  Package grub-efi-amd64 is not configured yet.

dpkg: error processing package grub-efi-amd64-signed (--configure):
 dependency problems - leaving unconfigured
No apport report written because the error message indicates its a followup error from a previous failure.
                                                                                                          Errors were encountered while processing:
 grub-efi-amd64
 grub-efi-amd64-signed
E: Sub-process /usr/bin/dpkg returned an error code (1)