Enter demo.kiwitalk.de, save, create appointment => works for me.
However, this system is really only for demo purposes, not for personal free use!
One more thing:
If you use your own Jitsi server, you secure the access via a JWT token. This way, no one else can use your system or enter a video call without authorisation.
If you then make the video calls via EGroupware, the name and avatar also come with the URL. You no longer have to enter this yourself.
Please show me your ping/mtr times IT=>DE.