Linux kernel extra modules for version 5.11.0 on 64 bit x86 SMP - broken package that cannot be fixed in Synaptic

Hope someone can help - complete novice at this and seem to be stuck in a loop. Running Ubuntu 20.04.3 LTS on a standalone laptop Have got a red 'no entry' type error message top right of my screen telling me that an error occurred and to run package manager. When I do that I get the message that I have one broken file 'Linux kernel extra modules for version 5.11.0 on 64 bit x86 SMP'. Fix broken packages appears to work, but the same error message just reappears after rebooting, and the same package is listed again as broken. I then tried removing the package (don't know if that is even wise!) which failed and gave the error message 'E: linux-image-5.11.0-25-generic: installed linux-image-5.11.0-25-generic package post-removal script subprocess returned error exit status 1' Thankfully, everything on my computer seems to be working fine, but I'd like to know what the problem is and how I might fix it if anyone has any suggestions. As I say, I'm a complete novice, so please keep it simple if you can. I think the error may have first occurred after an update, which usually run fine. Happy to provide any more info as needed. Thanks in advance

Output as requested by Thomas:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Correcting dependencies... Done
The following packages were automatically installed and are no longer required:
  libfwupdplugin1 libllvm11 shim
Use 'sudo apt autoremove' to remove them.
The following additional packages will be installed:
  linux-image-unsigned-5.11.0-25-generic
Suggested packages:
  fdutils linux-doc | linux-hwe-5.11-source-5.11.0 linux-hwe-5.11-tools
  linux-headers-5.11.0-25-generic linux-modules-extra-5.11.0-25-generic
The following packages will be REMOVED
  linux-image-5.11.0-25-generic
The following NEW packages will be installed
  linux-image-unsigned-5.11.0-25-generic
0 to upgrade, 1 to newly install, 1 to remove and 6 not to upgrade.
3 not fully installed or removed.
Need to get 0 B/9,978 kB of archives.
After this operation, 392 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
dpkg: linux-image-5.11.0-25-generic: dependency problems, but removing anyway as
 you requested:
 linux-modules-5.11.0-25-generic depends on linux-image-5.11.0-25-generic | linu
x-image-unsigned-5.11.0-25-generic; however:
  Package linux-image-5.11.0-25-generic is to be removed.
  Package linux-image-unsigned-5.11.0-25-generic is not installed.

(Reading database ... 239280 files and directories currently installed.)
Removing linux-image-5.11.0-25-generic (5.11.0-25.27~20.04.1) ...
/etc/kernel/postrm.d/initramfs-tools:
update-initramfs: Deleting /boot/initrd.img-5.11.0-25-generic
/etc/kernel/postrm.d/zz-update-grub:
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found background image: wallpaper.png
Found linux image: /boot/vmlinuz-5.11.0-34-generic
Found initrd image: /boot/initrd.img-5.11.0-34-generic
Found linux image: /boot/vmlinuz-5.11.0-27-generic
Found initrd image: /boot/initrd.img-5.11.0-27-generic
Adding boot menu entry for UEFI Firmware Settings
/etc/grub.d/35_fwupd: line 5: /usr/share/grub: Is a directory
run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 126
dpkg: error processing package linux-image-5.11.0-25-generic (--remove):
 installed linux-image-5.11.0-25-generic package post-removal script subprocess 
returned error exit status 1
dpkg: too many errors, stopping
Errors were encountered while processing:
 linux-image-5.11.0-25-generic
Processing was halted because there were too many errors.
E: Sub-process /usr/bin/dpkg returned an error code (1)