For example, lexemes don’t support labels, so they should not be a suggested entity type on Special:EntitiesWithoutLabels. See also parent task.
Note: there is a setting supportedEntityTypesForEntitiesWithoutTermListings for this, but this is something that should work in all Wikibase installations without the special setting, so we would like to solve this “properly”, and then probably get rid of that setting (T204711).
One fairly simple way to implement this is probably to create new entities of each type (BlankForm etc.) and check if they’re LabelsProviders.