I had got the impression this problem occurred on all mobile devices, not just iOS, since the thread didn't specify it only happened on iOS (or did I miss that?)
If it only happened on iOS, and that fixes it, then that's great! I guess mDNS helps establish local connections. Generally those experimental options eventually graduate to enabled-by-default, so hopefully that will just work out of the box in future.
I think it been a misunderstanding, what was fix it's that if you don't activate that feature "webRTC mDNS ICE candidates" then C3 Remote Preview it will never work as it happened with my iPhone6 for over three years it was OFF.
But Activating "webRTC mDNS ICE candidates" doesn't mean that C3 Remote Preview is gonna load fast all the Time because my other Phones all them had the "webRTC mDNS ICE candidates" =On all the time
So there are still some problems to resolve for C3 Remote Preview to load fast all the Time, we believe wen Chrome makes the connections it chooses the wrong "Candidates" making C3 load slow and this happens even when "webRTC mDNS ICE candidates" it's ON, it's like 50/50, fifty fast and fifty slow, it depends on the day.
Also, the thread is not only about iOS as we don't know what the other users which pones they have that reported slow Preview loadings, but I also don't believe we all have iOS if I'm not mistaking.
But you see only iOS mentioned on this thread because it's only me and Mikal making debugging and reporting back and he uses iOS for testing and I'm using iOS too, so maybe that's why you see all the time speak about iOS.
Will be nice if anyone that have problems with other phones like Android could report here so we can find a solution once for all, They where many that reported slow loading and voted for C3 local preview also but not sure which phones they have Android? iPhone?
If they could share their experiences will be grate.