Early builds of the MRTK supported Speech to Text but not the other way around. Many developers wanted a way to use Text to Speech, so Jared created a component and contributed it to the toolkit. This component is multi-threaded, supports multiple voices, integrates with Unity’s audio engine, and supports spatialization. It still exists in MRTK today. (Article, Source)

Azure IoT for HoloLens
An open source reference for connecting HoloLens to IoT devices that also became an official MS Learn Module.