Upgrade Ubuntu from a LTS Version to a none LTS Version
Upgrade Ubuntu from a LTS Version to a none LTS Version:
edit the file /etc/update-manager/release-upgrades and set
Otherwise you can only upgrade to another LTS Release.
Afterwards just do a normal
Important: Make sure screen is installed, so you can reconnect to the install if the connection gets lost. The ubuntu update does automatically create a screen session if it is available.