LWM2M-MQTT and MIMIC MQTT Simulator

Are you implementing LWM2M-MQTT in your environment?

MIMIC MQTT Simulator supports arbitrary payloads for MQTT messages
for a large number of simulated MQTT-enabled devices.

You can use it to quickly prototype your LWM2M-MQTT implementation.
In particular, you can test scalability of your LWM2M server over the MQTT
transport.

Check this 2-minute video that shows 2 sensors publishing unique telemetry
to Eclipse Leshan.