Does port 19302 for Google’s STUN need to be open?

Yes and No.

• Yes, port 19302 needs to be open for Edges using WebRTC. Edges use port 19302 to access Google’s STUN servers to get external IP addresses
  
  
• No, port 19302 is not required for WebRTC clients. Each WebRTC client requires a STUN response and will attempt to use Genesys Cloud STUN (UDP/3478) and Google STUN (UDP/19302) in parallel to determine its own external IP address. Only one successful response from either service is required. If port 19302 is not open, WebRTC clients can still succeed with STUN response from the Genesys Cloud STUN servers. Although the port 19302 is optional, there is no way to disable the requests.

For more information, see About ports and services for your firewall.