Drupal 8 Derative Advanced Menu Link Example

mymodule.links.menu.yml

mymodule_node_pages_links:
  deriver: \Drupal\mymodule\Plugin\Derivative\MyModuleMenuLinkDerivative
  class: \Drupal\mymodule\Plugin\Menu\MyModuleMenuLink

MyModuleMenuLink.php

<?php

/**
 * @file
 * Contains \Drupal\mymodule\Menu\MyModuleMenuLink.
 */

namespace Drupal\mymodule\Plugin\Menu;

use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Provides a default implementation for menu link plugins.
 */
class MyModuleMenuLink extends MenuLinkDefault implements ContainerFactoryPluginInterface {
  // Class overrides here.
}

MyModuleMenuLinkDerivative.php

<?php

/**
 * @file
 * Contains \Drupal\mymodule\Plugin\Derivative\MyModuleMenuLinkDerivative.
 */

namespace Drupal\mymodule\Plugin\Derivative;

use Drupal\Component\Plugin\Derivative\DeriverBase;
use Drupal\Core\Plugin\Discovery\ContainerDeriverInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\node\Entity\Node;

/**
 * Provides menu links of all Node entities with type "Page".
 */
class MyModuleMenuLinkDerivative extends DeriverBase implements ContainerDeriverInterface {

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, $base_plugin_id) {
    return new static();
  }

  /**
   * {@inheritdoc}
   */
  public function getDerivativeDefinitions($base_plugin_definition) {
    $links = array();

    // Get all nodes of type page.
    $nodeQuery = \Drupal::entityQuery('node');
    $nodeQuery->condition('type', 'page');
    $nodeQuery->condition('status', TRUE);
    $ids = $nodeQuery->execute();
    $ids = array_values($ids);

    $nodes = Node::loadMultiple($ids);

    foreach($nodes as $node) {
      $links['mymodule_menulink_' . $node->id()] = [
          'title' => $node->get('title')->getString(),
          'menu_name' => 'main',
          'route_name' => 'entity.node.canonical',
          'route_parameters' => [
            'node' => $node->id(),
          ],
        ] + $base_plugin_definition;
    }
    return $links;
  }
}

and for an external link, use:
'url' => 'https://external.url',
vs
'route_name' => 'entity.node.canonical',
'route_parameters' => [
'node' => $node->id(),
],