Awesome news ahead: LwM2M v1.2 specification is finally released! One of the headlining features of LwM2M v1.2 is LwM2M over MQTT! This is a good opportunity for LwM2M to get way more visibility, as MQTT (arguably the most popular IoT protocol) is currently missing any real data model.
LwM2M 1.2 feature highlights: 
State-of-the-art energy-efficient security—Leveraging (D)TLS 1.3 and Connection ID enhances security while reducing the challenges and energy losses of connecting devices over LPWAs like NB-IoT.
MQTT as a transport protocol—MQTT users can now add LwM2M device management functionality. Inversely, using MQTT as a transport mechanism for LwM2M simplifies connecting to the cloud in some scenarios.
Single-step device commissioning—Now, bootstrapping a device requires just a single bi-directional session instead of the previous five exchanges, saving time, energy, and other resources.
Optimized data reporting—LwM2M data-format optimizations shave bytes from each message, increasing energy-efficiency, device lifespan, and return-on-investment (ROI).
More details: New transports for LwM2M; this allows LwM2M messaging to be conveyed over MQTT and over HTTP. Optimizations for the bootstrapping interface; this reduces the amount of data and the number of messages transmitted during the bootstrapping exchange. Optimizations for the registration interface; this reduces the amount of data transmitted during registration exchanges. Optimizations for the information reporting interface; observation attributes may now be included in an Observe operation. Support for LwM2M gateway functionality; this allows non-LwM2M IoT devices as well as LwM2M devices behind a gateway to be connected to the LwM2M ecosystem and to manage those devices remotely. New, highly optimized encoding format based on CBOR called LwM2M CBOR. Enhanced functionality for firmware updates. Definition of new notification attributes (edge, confirmable notification, and maximum historical queue). Edge allows notifications to be triggered on rising and falling edges. Confirmable notifications allow the control of reliable transmissions of notifications. Maximum historical queue allows the control of time-series data usage. Clarifications of object versioning rules. Updates to use the latest communication security protocols based on TLS and DTLS 1.3 (as well as the use of the Connection ID). Flexibility to control the use of TLS and DTLS 1.3 through configuration information.
Untangling the relationship of security credentials and their server configuration.