Here is a curated list of the most active/relevant projects on GitHub
Azure IoT Hub Web Client
Based on the Paho MQTT JS client for web sockets, this web client allows to simulate an IoTHub device, sending telemetry, reading/writing properties, and respond to command requests.
It allows to connect using Shared Access Keys, and DPS.
Azure IoT Hub client based on MQTTNet for dotnet
Using a MQTT Library such as MQTTNet, this projects shows how to connect to IoTHub without using the official SDK.
WPF application, distributed as a .NET Core 3.1 global tool, to inspect MSIX/APPX applications deployed in Windows 10/11