https://github.com/matrix-org/matrix-rust-sdk

SDK is a library layer that hides the complexity of a thing inside an easier facade. It's exactly the right thing to do when the thing is a complicated one, but it also hints towards ... you know, the thing being complicated.

We haven't quite figured out whether a chat network needs to be as complicated as Matrix is under the hood. Could be that it does: federation, E2EE and the overall design of Matrix (it being a log propagator instead of a more traditional message passing system) increase the technical challenge by a lot, but then again, none of the three are essential (although undeniably useful in certain cases) for a chat network.