Even in the event of a disaster, push notifications are used to notify smartphone owners.
However, we have received requests from customers for an app that assumes that the LTE network is disconnected due to base station inconveniences during disasters, and communication from the Apple cloud cannot be considered. In that case, you would like to send push notifications to the iOS app on-premises within the customer's server, but there is a way to do that.
The answer you are looking for is Local Push Connectivity https://developer.apple.com/documentation/networkextension/local_push_connectivity
