With this snippet, you will be able to render a list of tags in Drupal 8.
use Drupal\taxonomy\Entity\Term;
use Drupal\Core\Link;
use Drupal\Core\Url;
$vocabulary_name = 'YOUR_VOCABULARY_NAME'; //name of your vocabulary
$query = \Drupal::entityQuery('taxonomy_term');
$query->condition('vid', $vocabulary_name);
$query->sort('weight');
$tids = $query->execute();
$terms = Term::loadMultiple($tids);
$output = '<ul>';
foreach($terms as $term) {
$name = $term->getName();;
$url = Url::fromRoute('entity.taxonomy_term.canonical', ['taxonomy_term' => $term->id()]);
$link = Link::fromTextAndUrl($name, $url);
$link = $link->toRenderable();
$output .='<li>'.render($link).'</li>';
}
$output .= '</ul>';
print $output;