You can try [hook_menu_local_tasks_alter][1]

    /**
     * Implements hook_menu_local_tasks_alter().
     */
    function mymodule_menu_local_tasks_alter(&$data, $route_name, RefinableCacheableDependencyInterface &$cacheability) {
      foreach ($data['tabs'] as &$tab){
        $tab['routing_name']['#link']['url'] = Url::fromUri('https://reset.my.password/');
      }
    }

  [1]: https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Menu%21menu.api.php/function/hook_menu_local_tasks_alter/8.2.x