rumqttc is a high level, easy to use client library that helps build applications which communicate over the MQTT protocol (commonly used in IoT devices). With this update we have been working towards making the client API a lot simpler and gradually improving/stabilizing v5 support.
Unrelated. The Wikimedia Foundation has actually documented the wprov query parameter. It's used to track the source of a link; "sfti1" is "Share a Fact on iOS for text shares, feature version 1".