I think what we’re seeing here isnt Valve messing up but rather the middle east conflict expanded to cyberspace and spilling over to impact civilians. Look at the timing and affected countries. China isnt also exactly known for free internet.

WebRTC works as fallback. WebRTC is encrypted and cant be used for much else.

STUN in the otherhand is unencrypted and the protocol itself can be used for DDoS reflection/amplification. I would not be surprised if this is somehow weaponized and/or blocked/analyzed in real time that then breaks the connectivity.