For WebRTC, the app connects directly to the Genesys Cloud WebRTC gateway. See this article for the ranges of IP addresses used by the Genesys platform: https://help.mypurecloud.com/articles/cidr-ip-address-range-for-cloud-media-services/
To debug the WebRTC connection, a tool is offered by Genesys on the below URL (attention - specific URL per region) https://help.mypurecloud.com/articles/run-the-standalone-genesys-cloud-webrtc-diagnostics-app/