The import option was not yet there. So I decided to make this myself. Now I am not a programmer, but for a hobby project like this I can do something. Fortunately, I have already taken a first step in reading OPML in the past, when I was working on a Pinboard project .
I could easily reuse that code. After a short read-in session in the way in which I can call the Aperture API, I now have a first, rough version . There is no categorization yet, no error handling, no validation by feed type (if needed) and it could be written a bit nicer. But it works!