i have managed to run background task on applicationWillTerminate but many time i failed to run background task especially when app is in the suspended (deactive) state. on applicationWillTerminate IOS wont wake your app and you cannot run any operations.

good question. you should execute leaveChannel method as background task, cause calling this method wont leave channel we see the following message in the logs "PTT leave request completed successfully, should be fulfilled soon" But the channel stays active in system ui. It might be a bug within Push To Talk framework. By the way When you kill Zello app the channel also removed.

dont expect the source code for example app as it requires actual ptt functionality like signaling, audio transmission client and backend functionality which is not part of Apple Push To Talk framework.

unfortunately audiosession handling is built in Push To Talk framework. in order to set different audio session category and mod wait for the framework to call channelManager(_:didActivate:)

Push To Talk is system ui framework with Audio Session handling and custom APNS feature. You need to develop backend ptt service like webrtc or better mediasoup.

if you mean IOS new Push To Talk framework then yes. But currently there is no much resource and tutorials.