@julian 1. Rocket.chat has been used for many years as a live chat in forums and social networks and has proven its effectiveness.
2. Nodebb is not a federated forum and the matrix protocol will never be needed. Although rocket.chat supports the federation.
4. Rocket.chat has more developers, which means there are fewer problems with support in the future.
5. You don't need to be a technical specialist to integrate with rocket.chat.
6. You don't need to learn other languages and technologies to support nodebb+rocket.chat.
7. Now rocket.chat is more stable than matrix/element and has many more functions and integrations. Matrix/element users constantly complain about errors and bugs.
I don't see any advantages of the matrix api for nodebb, now and in the long term