Having seen 2 messages about why and how backporting is done in the server, I opened this topic here (to be out of the PR chat).
You know there is typically one branch in the development where the main work is done. This is the master, main, trunk, or whatever called branch. Whenever a new stable release is created, a new branch is created from the current main branch. That way, a series of branches (called stableX) are created. For example with the release of NC 32, the branch stable32 was created.
Generally speaking, one typically only wants to implement things in only one location. That is, typically, one works on the main or master branch or whatever location represents the current development. Then, when a certain functionality is implemented, one can decide for which versions this is relevant. Then, this is backported appropriately.
We can discuss here further.
Chris