Hook not firing for custom entity -- how to set theme suggestions? I have an entity whose machine name is orb_act.  This code is not firing in Drupal 8:

/**
 * Implements hook_theme_suggestions_HOOK_alter().
 */
function mytheme_theme_suggestions_orb_act_alter(array &amp;$suggestions, array $variables) {

  // Add template suggestions based on the current view mode.

  $suggestions[] = 'orb_act';
  $suggestions[] = 'orb_act__' . $variables['elements']['#view_mode'];

}


How do I set my template suggestions?
The theme system doesn't know about entity types by default. You need to implement hook_theme() yourself at the moment. You likely also need a preprocess function to define a few standard things.

The console project generates this when creating a new entity type through it, you could try that to see how it looks. Otherwise look at what node module does in node_theme() and template_preprocess_node().