QtWebEngine is a very new module and since this forum is community driven, it'll need some time to build the knowledge around it. You can also check the interest mailing list for help.
Pointing the webkitwidgets browser example to html5test.com, it scored 0/20 in the 'Peer to Peer' section which includes WebRTC. The webenginewidgets browser example has partial support (scored 15/20) but I don't know if it would work for what you want. I don't think there's going to be future Qt development with Webkit.
