Symfony – Unable to find the object manager associated with an entity of class

I am trying to set whole registration process in my Symfony 6 project following the documentation.

I come to the part where I have a form that I am populating. When submited, I get an error:

Unable to find the object manager associated with an entity of class “AppEntityUser”.

I strictly followed the example that is given in the documentation.

And in my user entity:

/**
 * @ORMTable(name="`user`")
 * @ORMEntity(repositoryClass="AppRepositoryUserRepository")
 * @UniqueEntity(fields={"email"}, message="There is already an account with this email")
 */
class User implements UserInterface, PasswordAuthenticatedUserInterface
{
  ....

And in the doctrine.yaml file:

orm:
    auto_generate_proxy_classes: true
    naming_strategy: doctrine.orm.naming_strategy.underscore_number_aware
    auto_mapping: true
    mappings:
        App:
            is_bundle: false
            dir: '%kernel.project_dir%/src/Entity'
            prefix: 'AppEntity'
            alias: App

UserRepository:

/**


* @extends ServiceEntityRepository<User>
 *
 * @method User|null find($id, $lockMode = null, $lockVersion = null)
 * @method User|null findOneBy(array $criteria, array $orderBy = null)
 * @method User[]    findAll()
 * @method User[]    findBy(array $criteria, array $orderBy = null, $limit = null, $offset = null)
 */
class UserRepository extends ServiceEntityRepository implements PasswordUpgraderInterface
{
    public function __construct(ManagerRegistry $registry)
    {
        parent::__construct($registry, User::class);
    }
    ...

What am I doing wrong?