[jitsi-users] Multiple Network Interfaces Preventing Jitsi Call Connections

how common two-device systems are that do not have IPv6 enabled. This said,
I have no idea how to go about suggesting or accomplishing any of this, and
Jitsi does not have a public forum that assures search engine trawling. You
can understand why this would be important?

This type of fundamental errors typically provoke a "does not work, next".

Problematic NAT routers and XMPP services without jingle nodes
seem quite common as well, still, I found many many old reports on
ICE issues in the search results, but just no instruction to configure
fixed port(s), to allow forwarding specific ports to solve the router issue.
(Only did I find references to port settings in the skype preferences.)

But to make it simpler, jitsi could chose some fixed port numbers for
each installation, and suggest to configure the port forwarding
manually if UPNP configuration is disabled, no relay nodes are available,
and "ICE failed", or to set up a relay or to switch to a relaying service.

(My tests involved both, the very common "fritzbox" router that seems
to do problematic NAT, and a windows laptop with lan + wlan interfaces.
So I started to put together the info that was gathered here for the FAQ.