Even if your XMPP server does not support DataForm-based account registration (and you have open In-Band Registration, that may not be good as you do not have any protection against spammers creating account on your server), you can use submit, just pass a form with username and password fields filled in. Library will automatically detect that your server does not support DataForms and will use non-DataForm registration using values from username and password fields.

@hantu85 Is there a method that can be used for register account without the needs for passing a form for it where I need to register account with only username and password directly on the server without registration form to be filled.

You can always modify the source code of the library or pass the form (even if the server doesn't need it).

If not, you cannot use AccountRegistration(Async)Task, but you can implement task for registering an account yourself using register method of InBandRegistrationModule

Usage of form is preferred as now many servers provide captcha during registration (available only in forms) and with usage of form (as unified way to register the account) in the API is a simplification, as the client only need to implement registration using forms (transformation to/from old non-form-based mechanism is handled by the library).

@hantu85 When I tried to use the register method of InBandRegistrationModule and pass the registration info to it I got an error says remote-server-timeout