Report on who is subscribed to which notifications?

I’m trying to gauge how well my new Discourse forum is being used by people as a replacement for an email announcements list. I’ve created Announcement categories, with instructions for how to set notifications to get emails. I’d like to see how many people are using the notifications.

Is there a way to get a report on who has which kinds of notifications for particular categories?

On the admin dashboard you can run reports to see how many total emails were sent. This correlates pretty well with usage and notifications.

Beyond that you will probably need to run a Data Explorer query to get specifics.

Anyone want to help a newb with what such a query might look like?