EntityQuery condition "is not equal to..."
I found it !

I was not far away, I've just to reverse the last two parameters of the condition.

$query = \Drupal::entityQuery('node')
       -&gt;condition('type', 'order')
       -&gt;condition('field_multiple_choice', 'doe', '!=');
$nids = $query-&gt;execute();
$entities = \Drupal::entityManager()-&gt;getStorage('node')-&gt;loadMultiple($nids);



  As the doc says, public function
  QueryInterface::condition
  take following arguments :

condition( $field , $value = NULL , $operator = NULL , $langcode = NULL )