My Ubuntu (20.04) Software is prompting a new firmware available: UEFI dbx 77--> 217 (?), but when I try to update I receive the following error message:

Impossible to update UEFI dbx.

Blocked executable in the ESP, ensure grub and shim are up to date:/boot/efi/EFI/Boot/shimx64.efi Authenticode checksum [_checksum code_] is presente in dbx.

I am not really sure what this implies and, if I understood it correctly, why is it jumping from version 77 to 217. A bit more of details on the system:

$ lscpu

Architecture:                    x86_64

CPU op-mode(s):                  32-bit, 64-bit

Byte Order:                      Little Endian

Address sizes:                   39 bits physical, 48 bits virtual

CPU(s):                          12

On-line CPU(s) list:             0-11

Thread(s) per core:              2

Core(s) per socket:              6

Socket(s):                       1

NUMA node(s):                    1

Vendor ID:                       GenuineIntel

CPU family:                      6

Model:                           165

Model name:                      Intel(R) Core(TM) i7-10850H CPU @ 2.70GHz