Comment 6 for bug 1995753

In this case we identified due to recent package changes related to EFI.
at your own risk

sudo apt remove grub-efi-amd64-signed grub-efi-amd64-bin
sudo update-grub

Ubuntu upgrade error for grub-efi-amd64-signed : BinaryLane
https://support.binarylane.com.au/support/solutions/articles/11000095534-ubuntu-upgrade-error-for-grub-efi-amd64-signed

do not forget type 'Yes, do as I say!'.

$ sudo apt remove grub-efi-amd64-signed grub-efi-amd64-bin
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-5.4.0-125 linux-headers-5.4.0-125-generic linux-image-5.4.0-125-generic linux-modules-5.4.0-125-generic
Use 'sudo apt autoremove' to remove them.
The following additional packages will be installed:
  fwupd-signed
The following packages will be REMOVED:
  grub-efi-amd64-bin grub-efi-amd64-signed shim-signed
The following packages will be upgraded:
  fwupd-signed
WARNING: The following essential packages will be removed.
This should NOT be done unless you know exactly what you are doing!
  shim-signed grub-efi-amd64-signed (due to shim-signed)
1 upgraded, 0 newly installed, 3 to remove and 120 not upgraded.
1 not fully installed or removed.
Need to get 28.7 kB of archives.
After this operation, 16.3 MB disk space will be freed.
You are about to do something potentially harmful.
To continue type in the phrase 'Yes, do as I say!'
 ?] Yes, do as I say!
Get:1 http://nova.clouds.archive.ubuntu.com/ubuntu focal-updates/main amd64 fwupd-signed amd64 1.51~20.04.1+1.2-3ubuntu0.2 [28.7 kB]
Fetched 28.7 kB in 1s (25.5 kB/s)
(Reading database ... 237225 files and directories currently installed.)
Removing shim-signed (1.40.7+15.4-0ubuntu9) ...
Removing grub-efi-amd64-signed (1.173.2~20.04.1+2.04-1ubuntu47.4) ...
Removing grub-efi-amd64-bin (2.04-1ubuntu47.4) ...
(Reading database ... 236910 files and directories currently installed.)
Preparing to unpack .../fwupd-signed_1.51~20.04.1+1.2-3ubuntu0.2_amd64.deb ...
Unpacking fwupd-signed (1.51~20.04.1+1.2-3ubuntu0.2) over (1.27.1ubuntu7+1.2-2~20.04.1) ...
Setting up fwupd-signed (1.51~20.04.1+1.2-3ubuntu0.2) ...
$ sudo update-grub
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/50-cloudimg-settings.cfg'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.4.0-131-generic
Found initrd image: /boot/initrd.img-5.4.0-131-generic
Found linux image: /boot/vmlinuz-5.4.0-128-generic
Found initrd image: /boot/initrd.img-5.4.0-128-generic
Found linux image: /boot/vmlinuz-5.4.0-125-generic
Found initrd image: /boot/initrd.img-5.4.0-125-generic
done