The new Shadow server v2.4.0 brings TURN over TLS support for better firewall traversal of voice and video calls. This is fully optional and may be enabled in addition to (the default behavior) or instead of plain TURN.
Also, an autonomous Shadow proxy module (which is nothing else than an adapted version of Signal proxy) is now introduced – to be optionally used in conjunction with the Shadow server in scenarios when your Shadow server is inaccessible to users located in a certain administrative domain.