Register form custom submit

/**
* Implements hook_form_FORM_ID_alter().
*/
function mymodule_form_user_register_form_alter(&$form, FormStateInterface $form_state, $form_id) {
 $form['actions']['submit']['#submit'][] = '_mymodule_user_register_form_submit';
}
/**
* Custom submit handler for registration form.
*/
function _mymodule_user_register_form_submit($form, FormStateInterface $form_state) {
 $url = Settings::get('web_app_url') . '/home';
 $response = new TrustedRedirectResponse($url);
 $form_state->setResponse($response);
}