handleGetUnreadMessageCount is not implemented in Flutter iOS plugin in 6.x version. Is this by design or accident? It was implemented in 5.x version. When we updated we lost functionality.
https://github.com/apptentive/apptentive-flutter/blob/master/ios/Classes/ApptentiveFlutterPlugin.swift#L144
// Get the number of unread messages in Message Center
private func handleGetUnreadMessageCount(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
// TODO
}