Thank you for your detailed notes.

I changed the name from "Blockchain Core" to "Blockchain" instead of "Bitcoin".
I deleted the "armoryqt.conf".
I left "bitcoin.conf" being on its defaults.

Nothing changed. I tried variants with checking the "let armory ..." option, with unchecking it and both, using the "home dir" entry and not using it (leaving it empty).

Nothing worked.

I'm giving it up, now. I definitly am done with Armory.