Well you usually only need a STUN server that does the NAT hole punching, but transfers no data which can go directly P2P. The problem is that it doesn't work for two people on mobile data where a full TURN is needed. I've never completely understood why exactly it's broken in only that case, but it may have something to do with devices not being directly visible to each other for security reasons.
Or mobile operators being dicks because they can, that's frankly more likely.
> The problem is that it doesn't work for two people on mobile data where a full TURN is needed. I've never completely understood why exactly it's broken in only that case
This is not the only case where it doesn't work. One of the experiments I tried was desktop computer on fixed broadband connecting to another desktop computer on fixed broadband.
Hmm I suppose there may be edge cases where it doesn't work for home networks, but I doubt it's more than a few percent of users. For mobile data it's broken for 100% of devices.
> For mobile data it's broken for 100% of devices.
No, it's not. I've run my own webrtc signaling and STUN servers, and trying between multiple different mobile operators and devices I can establish a connection without TURN in most cases. Not 100% but in most cases.
Or mobile operators being dicks because they can, that's frankly more likely.