Add system image error: grub configuration /dev/mem operation not permitted

Yes, you definitely need to try.
For test I successfully update LTS 1.2.2 to the latest rolling

Do you want to continue without signature check? (yes/no) [yes] 
Checking MD5 checksums of files on the ISO image...OK.
Done!
What would you like to name this image? [1.4-rolling-202102141111]: 
OK.  This image will be named: 1.4-rolling-202102141111
Installing "1.4-rolling-202102141111" image.
Copying new release files...
Would you like to save the current configuration 
directory and config file? (Yes/No) [Yes]: 
Copying current configuration...
Would you like to save the SSH host keys from your 
current configuration? (Yes/No) [Yes]: 
Copying SSH keys...
Running post-install script...
Setting up grub configuration...
Done.