How to upgrade 15.10 to 16.04?

Question

ubuntu

Trying to upgrade to 16.04 from 15.10
`do-release-upgrade` gives
Checking for a new Ubuntu release
No new release found
`update-manager` also fails with
The software on this computer is up to date
`apt-get update` message did

Answer 1

You need to boot from a disk or flash drive with Ubuntu 16 and select the system update there.

Answer 2

Forced method, tested on myself when similar methods as written to your question did not work:
sudo sed -i 's/wily/xenial/g' /etc/apt/sources.list
sudo apt-get update
sudo apt-get dist- upgrade

Answer 3

sudo apt-get update && sudo apt-get dist-upgrade
sudo reboot
sudo update-manager -d

Answer 4

Kubuntu not coming on 16.04, only 15.10? Read comments

Answer 5

Either wait for Canonical to decide that the system has stabilized enough to upgrade users, or
sudo do-release-upgrade -d