09-24-2018, 05:18 AM
Update: It is possible. Read /var/log/dist-upgrade/main.log which showed a note about ubuntu-desktop. Google revealed having more than one desktop manager (mate-desktop and ubuntu-desktop) confuses the upgrade. Uninstalled ubuntu-desktop and retried was able to go through 'do-release-upgrade'. Now on 18.04, though by screen is blank after reboots, can access via SSH. One problem at a time I guess.