Pathauto

You can use the following code snippet to change the required attribute of the path field in the node form alter in this way:

/**
 * Implements hook_form_FORMID_alter().
 */
function example_module_form_node_form_alter(&$form, &$form_state) {
  $form['path']['widget'][0]['#open'] = TRUE;
  $form['path']['widget'][0]['alias']['#required'] = TRUE;

}

This will keep the path tab open by default and mark the alias field as required.

You can use the following code to set URL alias for a node if your website also uses Pathauto

 $node->path = [

      'alias' => '/' . $node_url,
      'pathauto' => Drupal\pathauto\PathautoState::SKIP,

];
    $node->save();

Where $node_url is the desired alias and $node is loaded node object.