Can I push notify based on geo-fencing without an iOS App?
No. Apple includes find my phone and friends which lets the owner of the device set up geo fences with notification when those devices a device has permission to track cross a geofence. There is no hook to automate what you contemplate as the device just receives a notification. 

Similarly, the workflow automation let’s you get a location but not set up geofence push notifications. 

You need to make or use a third party app to use location notifications and APNS as you requested on iOS 12 and below. 

To achieve your goal without an app, convince Apple this needs to be added to the OS and to the workflow app to have geolocation triggers.