I do understand that Apple emphasizes security but I have to ask: is there any way that a 3rd party app can access all notification data? Like the NotificationListenerService
available in the Android API?
I did come across ANCS, but I guess that's only accessible to BLE devices. Please tell me I'm wrong.
No, Apple does not provide access to the Notifications of other apps, nor does it provide access to any listener service, or notification queue.
Here is a link to the Apple doc, which describes the provisioning that is required to set up and access APNS: APNS Provisioning and Development