Dear Olf, unfortunately, it is impossible to provide the old imports in the infrastructure that we have. I have not designed my scripts, nor distribution path, nor OSM Scout Server with that in mind. As a result, we can provide one set of maps and that set has to be imported in one go. There is a handling of switch over from one set to another, but nothing more fancy. So, to start mixing imports, some new development has to be undertaken.

In retrospect, maybe I should have looked further when implementing maps distribution and used some packaging format for it. However, again, that requires some serious time investment. Something I am not planning as a priority, when you look into long least of issues to resolve.

Supporting old SFOS versions is not super easy due to changing names of dependencies, improvement of the tools (gcc and friends) and so on. Right now there are no changes in database formats, but at some it may come as well, which would make use of old server impossible with new maps. So, even with OBS builds, you should expect sunset for older SFOS versions in terms of support. But that, I believe, has been discussed earlier as well.

As for libosmscout library support, if you do prefer to use that, it is possible to switch to Karry's OSM Scout application. It surely is better than use of libosmscout backend on OSM Scout Server. Don't know how it supports old SFOS versions, but maybe grabbing older version would work.