mbedTLS + NUCLEO-F401RE + SIM800

Hi Dimitris,
As you can see, error -0x7080 is MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE which is returned by several locations, when a requested feature is not supported. Usually it is a configuration issue. This is not related to the platform, or the entropy source (though you do need an entropy source to the functionality).
I would suggest you look at the debug logs for you to understand where this error is returned, and then you could configure the relevant feature if possible.
Regards,
Mbed TLS Support
Ron