T159795: Port Translate to new RC Filters system mirgated older filters in Translate ("Not in translation namespaces" etc.) to the (then-) new recent changes filter system, but T369058: Move Recent Changes Language filter from Clean Changes extension to Translate brought new filters (not enabled by default) to Translate extension. (the language filter mechanism is not yet removed from CleanChanges, but is disabled in translatewiki)
The image below comes from T413769: Replace Translate's language filter on Special:RecentChanges with Lookup Language selector:
The goal of this task is the "Language filter" not be an individual component; it should be integrated to the main filter system.
("User filter" is not concerned here since it is not part of Translate extension; see T167224: Implement 'User' filters and filter menu in the new UI instead.)
