Since build 2.6.10 iOS SDK is shipped with WebRTC framework patched to prevent microphone permissions request while playing WebRTC stream on iOS 14.
Nested framework issue workaround in builds before 2.6.86
WebRTC framework is nested which may lead to AppStore publishing issues. To workaround this, move WebRTC framework to the same level as FPWCSApi2.framework or FPWCSApi2Swift.framework
Since build 2.6.86, WebRTC library is shipped as a separate framework, so the workraround is not needed any more.
See details about using frameworks in application here
Echo cancellation while publishing WebRTC stream
Echo cancellation is enabled by default in WebRTC framework shipped with iOS SDK. WebRTC framework does not provide any settings to disable echo cancellation.