I finally managed to install jitsi using the quick steps.
I think you should underline a little bit more that the installation must be done on debian 8 and not debian 7.
Now, I activated webrtc in jitsi-meet.
I've got several problem:
First: I can't see the video from the guest I invited (and the guest doesn't see the video). This is not related to webrtc. The problem was present before the webrtc activation.
Second: when I try to share a desktop: nothing happens (I tried with chrome and firefox).
Third: when I use firefox, a plugin is required but the message is not clear at all and the link to the required plugin is missing.