I have developed WNS in Xamarin mobile app to receive raw push notification successfully (wihout using Azure Notification Hub) , however i am looking for a feature wherein mobile apps can subscribe to specific topic and from backend admin can send notifications on that topic to broadcast the alerts.
i tried to searched for tag based notification in UWP but i always come across Azure Notification Hub sample
here is the link to Azure Notification Hub Tag based
Is there anyother way wherein admin can broadcast the notifications without the use of Azure Notification Hub ?
You will have to go through the following doc: Windows Push Notification Services (WNS) overview. Define your own service, which will then send post to WNS for push notifications. As a example, see this quick start
And as for your specific scenario, if you only need "subscribed devices can receive the notifications", you can define the logic in your own backend app. Then only send post request to WNS for subscribed devices.