Get array of all entities from entity reference field
I can't say for sure on that specific field but usually there's the referencedEntities() method you can call

https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Entity%21Entity.php/function/Entity%3A%3AreferencedEntities/8.4.x

So something like this perhaps:

$entities = $node->field_taxonomy_term->referencedEntities();