drupal 8 get all nodes of type
$nids = \Drupal::entityQuery('node')->condition('type','my_custom_type')->execute();
$nodes = \Drupal\node\Entity\Node::loadMultiple($nids);
Source: drupal.stackexchange.com
$nids = \Drupal::entityQuery('node')->condition('type','my_custom_type')->execute();
$nodes = \Drupal\node\Entity\Node::loadMultiple($nids);