I've written an app that uses Firebase (if that's relevant) and is targeted to users residing within a certain city (Strasbourg, France, in my case). Also, users will log into the app using an email address (Gmail or other). How can I make sure only people residing in Strasbourg install the app? I can't use private distribution, since I don't have a list of user email addresses and anyway they are not part of my organization. Ideally, I'd like to be able to offer the app on Google Play, rather than, say, uploading the app to Google Drive and then sending them a link when they request it.
I decided to abandon this idea because it would prevent people who are temporarily away from their home in Strasbourg from being able to download the app and that disadvantage would outweigh the benefit of keeping "outsiders" out of the app community.