I wish you could follow duplicates of radars like in github.. That issue was "resolved" by saying its a duplicate of issue 29281220, which isn't helpful at all. That issue could be even older than the one you linked.
If this is something you care about, you should file an enhancement request, even if you write that it is a duplicate of that issue yourself.
Right now, WKWebView and SFSafariViewController (and the authentication service variant, and Web.app which is used for shortcuts on the home screen) do not have WebRTC support - only MobileSafari.app does.