Linux

Debian has two main versions, stable - which is released every two years and supported for a long time. And unstable which is basically a rolling release and constantly changes adopting things to test them before the next stable release. There is also testing, but that is just to place thing in before promoting them to stable so has the same release cadence as stable.

Two years of fixed versions on a desktop is a very long time to be stuck on some packages - epically ones you use regularly. Most people want to use things that are newer then that, either new applications released or new features for apps they use in the past two years.

Ubuntu also has two release versions (that not really the right term though). They have a LTS version which is released every two years much like Debian is. But they also have a interim release that is released every 6 months. This gives users access to a lot newer versions of software and stuff that has been released more recently. Note that the LTS versions are just the same as the interim versions, its just that LTS versions are supported for a longer period of time, so you can use it for longer.

For the Ubuntu releases they basically take a snapshot of the Debian unstable version, and from that point on they maintain their own security patches for the versions they picked. They can share some of this work with Debians patches and backports, but since Debian stable and Ubuntu are based off different versions Ubuntu still needs to do a lot of work with figuring out which ones they need to apply to their stuff as well as ensuring things work on the versions they picked. Both distros do a lot of work in this regard and do work with each other where it makes sense.

Ubuntu also adds a few things on top of Debian. Some extra packages, does a few things that make the disto a bit more user friendly etc.

Any other distro that wants to base off one of these has to make the choice

• Do they want a very slow release cadence matching Debian (or Ubuntu LTS).
• Or do they want a faster release cadence of Ubuntu without doing much extra work as they can build off the work that Ubuntu is doing on top of Debian.
• Or do they want to take on all that extra work themselves and have more control over the versions included in their repos.

For a lot of distro maintainers basing off Ubuntu gives them a newer set of packages to work with while doing a lot less work doing all that work themselves. Then they can focus on the value adds they want to add ontop of the distro rather then redoing the work Ubuntu already does or sticking with much older versions.

The value add work that needs to be done on either base I dont think is hugely different. You can take the core packages you want and change a few settings, or remake a few meta packages that you dont want from Ubuntu. This is really all stuff you will be doing which ever one you pick. It is a lot more work keeping up with security patching everything.