Schema for group module
The RDF UI module only provides the 'RDF Mapping' local task for nodes at the moment (so not Group entities). See the if statement in this snippet from Drupal\rdfui\Plugin\Derivative\RdfUiLocalTask::getDerivativeDefinitions():

foreach ($this-&gt;entityManager-&gt;getDefinitions() as $entity_type_id =&gt; $entity_type) {
  if ($entity_type-&gt;get('field_ui_base_route') &amp;&amp; $entity_type_id === "node") {

    $this-&gt;derivatives["overview_$entity_type_id"] = array(
      'route_name' =&gt; "entity.$entity_type_id.field_ui_fields",
      'title' =&gt; $this-&gt;t('Fields'),
      'parent_id' =&gt; "field_ui.fields:overview_$entity_type_id",
    );

    $this-&gt;derivatives["rdf_$entity_type_id"] = array(
      'route_name' =&gt; "entity.$entity_type_id.rdf_ui_fields",
      'weight' =&gt; 2,
      'title' =&gt; $this-&gt;t('RDF Mappings'),
      'parent_id' =&gt; "field_ui.fields:overview_$entity_type_id",
    );

  }
}