2. If you're using the built-in TURN server behind NAT (not recommended), you need to set up hairpinning in your NAT. I don't see any good way around it. Please mention it in the README.
I have added the following warning.
WARNING : as the default installation will install a turn server (coturn) on the same machine as galene, you might possibly face problems if hairpinning is not set in your NAT. Some options of coturn server are supposed to solve some of them but it is not clear that it will always work. Nevertheless, the script can easily be adapted in order to use an externat turn server. For the time being it has been successively tested on a public cloud (Scaleway) and behing a 10 years old freobox (v6).