If you are trying to upgrade Mate 16.04 to version 18.04, yes "do-release-upgrade" does work. The size of the boot partition does need to be increased. See graf_eberstein's thread:
He discusses the need to enlarge to boot partition and ways to do it. I simply used gparted to enlarge the boot partition. His thread also discusses step-by-step instructions on how to upgrade from 16.04 to 18.04. It all worked for me best starting with a clean install of 16.04.