For those of you who may be stuck on an older version of Ubuntu Linux, such as 16.04 or 16.10, and wish to upgrade to the latest release, here is one solution.
A few weeks ago, I attempted to upgrade to Ubuntu Linux 17.04 and received the following message:
Checking for a new Ubuntu release
No new release found
So as it turns out, you can change the following configuration file located here:
Simply change the line
After that, run "sudo do-release-upgrade;" again, and hopefully you'll be able to upgrade!
Don't forget to backup all your data first!!!