All classes that implement LanguageSwitcherInterface in Drupal 9
- class \Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationContentEntity implements OutboundPathProcessorInterface, ContainerFactoryPluginInterface, LanguageSwitcherInterface
- class \Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationSession implements OutboundPathProcessorInterface, LanguageSwitcherInterface
- class \Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUrl implements InboundPathProcessorInterface, OutboundPathProcessorInterface, LanguageSwitcherInterface