Hi,
1) The LwM2M sample app uses the function nrf_inbuilt_key_write() in nrf_inbuilt_key.h to store keys for DTLS
2) The Zephyr LwM2M implementation uses function tls_credential_add() in net/tls_credentials.h to store keys for DTLS (see function load_tls_credential() in lwm2m_engine.c). This way of handling keys is disabled/overrided in the lwm2m sample app.
I tried to use method #2 in the LwM2M sample app but did not get it to work.
Please clarify how the two different key management methods are related to eachother! Does only method #1 work with nRF9160?
BR / Björn