Ventsharm can you describe what use case you are trying to achieve?
By ID verification you mean just checking the user is registered, checking that the user is part of a predefined list of users, or do you mean a full-fledged ID card scanning solution to validate the age of users?
Did you write the blog article you are linking to? It seems like you already have a solution, what is the problem? Or if that's not your text/implementation, why wouldn't that work for you?
If you are hosting your forum on FreeFlarum, even if another extension existed for your use case it might not be certain to become available. You might be better hosting the forum yourself, particularly if handling adult content.