Get enabled content types machine name
Okay, I don't know how I missed this.

/** @var \Drupal\group\Entity\GroupType $group */
$group = GroupType::load($groupKey);
$plugins = $group-&gt;getInstalledContentPlugins();
foreach ($plugins as $key =&gt; $plugin) {
  $bundle = $plugin-&gt;getEntityBundle();
}