The good news is: Remote Access works - with Domain provided by deSEC behind Router Fritz.Box 7590.
The status messages A are : “Successfully resolved” for [IP4] and IP6]
My question: under Nextbox App Remote Access HTTPS/TLS Status:
How should I deal with these status messages B:
"Failed reachability for: [external IP], [Domain dedyn io] for [IPv4]
"Failed reachability for: [external IP], 1 for [IPv6]
The given references to the docs nitrokey com / nextbox
Port-Forwarding for [IPv4] and
DNS-Rebind for [IPv6]
are taken into account as far as possible.
Thanks for your kind support