As I understand it, it’s an eM Client problem, because it treats LABEL as a separate address. Please follow up here: https://forum.emclient.com/t/contacts-wont-display-address-in-column-when-vcard-uses-lower-case-type/45285/7

@rfc2822 Ich werde mich mal an den eM Client Support wenden. Mal sehen, was die sagen.
Melde mich wieder, wenn ich eine Antwort habe. Sollte dabei nichts rauskommen, kann ich ja mal noch die Debug-Logs, etc schicken.
Erstmal vielen Dank!

Thanks mate, your hint led me to the solution.
I had to remove the %20 out of the ORGANIZER property. i.e. i changed the Account Name on DAVdroid from “Idefix Kalender” to “IdefixKalender”
I works

Obviously eMClient does not like the %20 as that is invalid for mail addresses.

Thanks