It is an independent chapel with the pre-1962 TLM. Under no bishop. They used to have a picture of the Pope in the entrance to the chapel, but none since Bergolio. Those who are sedes keep quiet about it.
I'd be interested to know if their Masses are
una cuм or
non una cuм, and which bishop comes there for confirmations, provides their oils, and so on. It's a legitimate question.