The broadcast option of Traktor3 Pro is using the icecast2 protocol. Traktor 3 Pro fails to connect to the latest versions of icecast2 ( https://icecast.org/ ) and liquidsoap ( https://www.liquidsoap.info/ ) using the icecast2 protocol that is defined here: https://gist.github.com/ePirat/adc3b8ba00d85b7e3870
The issue is that in the communication to icecast or liquidsoap, Traktor PRO will only respond to a "HTTP/1.1 200 OK" message, and not a "HTTP/1.0 200 OK" message as defined by the standard. The different is only one small minor number, however its the reason it fails to connect.
Support has told me that NI will remove the broadcast functionality in future versions, advise me to use some complicated setups with small helper applications that would take over the broadcasting functionality.
They also refused to give me a refund for this DJ software that is useless for my purpose.