INFO [socket_c2s-thread-3]: org.jivesoftware.openfire.spi.RoutingTableImpl - Will not route: Remote domain internal.auth.mydomain.com is not accessible according to our configuration (typical causes: server federation is disabled, or domain is blacklisted).
Getting Jitsi Meet to work with another XMPP server than the one that they’re using is hard. They have not made a solution that aims to be portable. It is possible, however: we have the ofmeet plugin that does exactly that.
The error message seems to indicate that you need a conference service called ‘internal’. You can check if you have one, by going to the admin console, and navigate to the summary of all conference services: Group Chat > Group Chat Settings > Service Summary
The default conference services that I expect to be there is called ‘conference’. You will need to create another one, called ‘internal’ to work around the particular error that you show.
I do not know (but I suspect not) if this is the only issue that stands between you and a functional integration. As I said, this gets tricky, fast.