All classes that implement FallbackPluginManagerInterface in Drupal 10
- class \Drupal\Core\Block\BlockManager implements FallbackPluginManagerInterface, BlockManagerInterface uses CategorizingPluginManagerTrait, FilteredPluginManagerTrait
- class \Drupal\Core\Entity\EntityReferenceSelection\SelectionPluginManager implements FallbackPluginManagerInterface, SelectionPluginManagerInterface
- class \Drupal\Tests\Component\Plugin\StubFallbackPluginManager implements FallbackPluginManagerInterface
- class \Drupal\filter\FilterPluginManager implements FallbackPluginManagerInterface
- class \Drupal\views\Plugin\ViewsHandlerManager implements FallbackPluginManagerInterface