children
A more Drupal way of getting the children of an element using the element_children method instead of simply stripping the hashes
In the php template you would do something like this.
<ul>
<?php foreach(element_children($content['field_myfield']) as $key): ?>
<li><?php print render($content['field_myfield'][$key]; ?></li>
<?php endforeach; ?>
</ul>
You can loop on a render array with native twig, as it will render properties.
<ul>
{% for element in children(content.field_myfield) %}
<li>{{ element }}</li>
{% endfor %}
</ul>