<?php

/**
 * Implements hook_form_alter().
 */
function MY_MODULE_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  # Обработчик для автоматического заголовка формы.
  if($form_id == 'node_my_type_form') {
    $form['actions']['publish']['#submit'][] = 'hook_my_type_form_submit';
  }

}

function hook_my_type_form_submit($form, FormStateInterface $form_state) {
  $form_state->set('title', 'Hello world');
}