grub-efi-amd64-signed … Sub-process /usr/bin/dpkg returned an error code (1)

I have xubuntu

Every time I install something, I get an error. I think it is relating to grub-efi-amd64-signed? I have tried to reinstall grub but that didn’t help.

(I am not very experienced at all so there is a big limit to what I can confidently do. I have not tried to force as recommended here Grub error whenever installing anything because it already asked me to type in “Yes, I want to do this” to remove grub, so maybe I already reinstalled it ok, although I am not sure.)

dpkg: error processing package grub-efi-amd64-signed (--configure):
 installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 255
Setting up libgegl-dev:amd64 (0.3.30-1ubuntu1) ...
Errors were encountered while processing:
 grub-efi-amd64-signed
E: Sub-process /usr/bin/dpkg returned an error code (1)