Matrix[1] has an encryption scheme based on the Signal double-ratchet (which was based on the OTR scheme) called Olm, and is completely federated with an open standard. So you can run your modified version, and be the only person who keep a history of your conversations (only the homeservers that participate in a conversation store the chat history).
Matrix also has features like bridges to other chat systems, as well as a plethora of clients thanks to being an open standard (the most popular is Riot).
[1]: https://matrix.org/