As far as I understand, they want to make Nostr a universal protocol for everything, including personal correspondence. At this point, I don't think it's sustainable. It's still a very young protocol, and it has a lot of privacy issues to solve. But even after that, I think it's better to use ready-made solutions for private chats such as SimpleX, for example. Not advertising.

This is a young open source project. The cool thing about it is that it's the only messenger that doesn't have user IDs like most private messengers have.