As there is no possibility to select a certificate that is already on the device when configuring OpenVPN from the RMS (see Configure OpenVPN Client via RMS when key material is already there - #3 by Justinas ), I am now configuring my OpenVPN connections via WebUI and have thus not encountered this issue any more. I guess this was just a beginner kind of “holding things wrong” and I will revisit this issue once it has become possible to configure an OpenVPN connection via the RMS.
Consider this issue solved, please.
Greetings, Marc