Ubuntu is a point release distro, meaning that it has multiple releases that you update between. However, there are many people who would instead prefer to have a rolling release distro, where there is one release that gets continually updated. While some people would move to another distro, like Debian Sid, or even Arch Linux, there is a way that you can turn Ubuntu Linux into a rolling release distro. The method that I am going to show you today, it a lot faster than doing it manually, and it entails downloading a shell script which will automatically change you to the ‘devel’ release.
The whole ‘devel’ thing has been half-broken in one way or another since it was introduced. My advice is just to not use it. And I honestly think we should remove all remnants of it from launchpad and the Ubuntu/PPA archives as well. Trying to treat “the latest at any given point” as the same thing as a “rolling” distribution may have been fun to score some political points, but it doesn’t actually do useful things.
As someone wrote in 2017 at Ubuntu Bug #1728616: using ‘devel’ in sources.list causes apt-get update to fail [via]:
Looking at the issues for “rolling-rhino” it looks like that is still the situation today.