One and two read as if STUN and TURN are specific technologies build for WebRTC, but as far as I know, those are just the standard technologies for handling P2P

One and two read as if STUN and TURN are specific technologies build for WebRTC, but as far as I know, those are just the standard technologies for handling P2P-scenarios with consumer level usability in mind. I think the biggest issue is that often you have to set up a STUN/TURN server in an extra environment. In the XMPP world, ejabberd has come to the point, where it brings most things you need today in a single package (XMPP, HTTPS, Lets-enrypt, STUN/TURN, ...). That way you add about 5 lines to a config file and get STUN and TURN with little effort. I like that simplicity and if you don't, you are still free to use an external STUN/TURN server.