I have a client who I'm pretty sure is behind a double NAT. No WebRTC things work for them (tried Jitsi Meet and GoToMeeting) and I suspect their network setup. Is there any good way to debug this situation or to work around it so they can use WebRTC?
(Reason for double NAT is: ISP-level NAT + probably in-home NAT. Client is remote so I cannot directly verify their hardware setup.)