While hundreds of Facebook groups and Discord servers have already been created since Harry Potter Wizards Unite was announced, developers Niantic have just announced the formation of an official community on their website.
For the moment, it takes the form of a forum, where you can discuss various topics, see announcements and find answers to popular questions.
Remember, when signing up you need to use the same account that you use to sign in to the game!
Feel free to take a look around!