I have the same Problem I tried out all over 5 hours
But the internal Connection in other Subnets local works but extern its called no opened Channel, I give up to work with Jitsi, I host Asterisk / Coturn with Matrix Synapse all works fine here but Jitsi already stress my mood
Edit my Videobridge takes not the Config from env,
just added in jvb.sh
and created the config dir relativ and pu the sip-communicator.properties there this was my fix, because I don’t used the installed Packages for Debian, just put my Stuff in /opt with a own Systemd but now all seems to work fine!