Custom Form Password Authenticator return only UserInterface symfony
You probably have something confused.
The AdvancedUserInterface - indicate user instance, and extends from UserInterface.
The UserProviderInterface - indicate of providers for loads users (UserInterface).
In method loadUserByUsername you can returns AdvancedUserInterface instances.
As example:
User:
class User implements AdvancedUserInterface{ // .. Some fields and functions}User Provider:
class MyUserProvider implements UserProviderInterface{ public function loadUserByUsername($username) { // Get the User instance from DB or another system return $user; } // Some functions}