Thank you very much for this.
You know, I was doing this and other explanations, and I was always hitting the same wall: no webrtc stream, only MJPEG.
But it seems that Home Assistant for Mac (the app) doesn’t support webrtc.
So, indeed, all what I was doing (and what you describe as well) works perfectly fine on the iPhone and on the web-based version of Home Assistant, but I was just testing it on the App 
Hours wasted trying it on an app that is unable to render webrtc video! 