The .NET based OPC UA SDK allows for the new OPC UA Publish/Subscribe communication pattern. With that you can send data to Broker and Cloud, but also can subscribe to OPC UA data set published via MQTT broker.

The PubSub-AddOn contains the JSON encoder/decoder supporting both the CompactEncoding and the VerboseEncoding running over transport binding to MQTT protocol. The UA Binary encoder/decoder, with UADP encoding and the UDP transport binding supports the unicast, multicast and broadcast messages, but can also use the MQTT transport binding.

The beauty of this solution is the simple (4 lines of code) integration in case you already have the .NET based Client/Server package. You can extend without changing your existing code.