Load node entities by owner

I want to load entities by their owner. This is what I have so far:

\Drupal::logger('migrate_users')->notice("Hello start");
$userStorage = \Drupal::entityTypeManager()->getStorage('user');

$query = $userStorage->getQuery();
$uids = $query
  ->condition('status', '1')
  ->condition('type', 'student')
  ->execute();

$users = $userStorage->loadMultiple($uids);

// help regarding this line
$entities = \Drupal::entityTypeManager()
  ->getStorage('node')
  ->loadByProperties([
      'type' => 'article',
      'user' => SOME_USER,
    ]);

\Drupal::logger('dssi_migrate_users')->notice("done");

What do I need to pass in for SOME_USER?

You are only using the wrong property name for passing the user ID.

The following would work:

$entities = \Drupal::entityTypeManager()
  ->getStorage('node')
  ->loadByProperties([
      'type' => 'article',
      'uid' => SOME_USER_ID,
    ]);

If you wish to fetch entities from several users, just use an array:

$entities = \Drupal::entityTypeManager()
  ->getStorage('node')
  ->loadByProperties([
      'type' => 'article',
      'uid' => [uid1, uid2, uid3],
    ]);

loadByProperties() method use buildPropertyQuery() to pass the values to the query, which use a "IN" condition.

What you are looking for is IN operation and I think loadByProperties method only acts on Equals operation so, use getQuery method instead and you can attach as many conditions as you want, like below:

$nodeQuery = \Drupal::entityTypeManager()->getStorage('node')->getQuery();
$entities = $nodeQuery->condition('bundle', 'article')->condition('uid', $uids, 'IN')->execute();