In my experience you typically don't need STUN for that to work - the ICE flow of WebRTC will handle regular NAT[1].

It's typically when ICE can't determine the first few steps (eg your public address) that you need STUN to help you out.

TURN tends to be needed in hostile networking situations like double NAT'd networks or very restricted networks like hospitals.

[1] - https://webrtcglossary.com/ice/