We offer simple email and password auth and also manage session tokens in the most secure way possible. We're free, built for and by developers (who have had to struggle with auth several times in the past). Our solution is modular and easy to implement.
The docs for non-standard cases is very poor, and Python SDK has some weird quirks. For example, for some reason you have to use different methods to get user info depending on how user registered (via email or via google oauth).
However, basic cases on frontend are super-easy to implement.