For testing, a service could actually be useful. But filtering notes tagged by a third party should be definitely more complex, right?
Not really. I would do a service that creates 1985 tags with the language code using the same created_at the tagged post has. Then a client can just do a REQ for the latest 1985 tags and load all the event ids individually. A webpage could easily do that and I think it would work on Coracle right now, without any changes.
> and load all the event ids individually So two REQ instead of one. I am happy if this is not a burden.
These days almost anything in Nostr is 3-4 reqs away...