How to get all node entities tagged with a specific term? For a given taxonomy term in D8, is there any API function/method that returns all node entities that reference it?
You can use loadByProperties() to get all node entities that reference $term_id:

$nodes = \Drupal::entityTypeManager()-&gt;getStorage('node')-&gt;loadByProperties([
  'field_tags' =&gt; $term_id,
]);