<?php
// Programmatically create and translate menu links.
use Drupal\menu_link_content\Entity\MenuLinkContent;

$menu_item = MenuLinkContent::create([
  'bundle' => 'menu_link_content',
  'langcode' => 'en',
  'title' => 'My menu link',
  'description' => 'My description.',
  'menu_name' => 'main',
  'link' => [['uri' => 'internal:/taxonomy/term/15']],
  'parent' => 'menu_link_content:c8859c9c-a550-45a9-a705-5d032dee525c',
  'weight' => 0,
]);
$menu_item->save();

$menu_item_es = $menu_item->addTranslation('es');
$menu_item_es->title = 'Mi enlace del menú';
$menu_item_es->description = 'Mi descripción.';
$menu_item_es->save();