I have a related question to the OP.

What security would you recommend to run on an unreliable connection?

To be specific, I have IoT devices which connect to the cloud using MQTT-SN. We use MQTT-SN because the underlying connection is NB-IoT (required for high penetration into difficult to reach areas). The latency on NB-IoT is quite high, which can lead to problems with TCP timeouts - so we have been recommended by the network operator to use UDP not TCP, which in turn leads to MQTT-SN, as it supports QoS 0 (unacknowledged).

But we are also very aware of security issues - so how would you put something like TLS onto a UDP datastream?