During the TLS handshake, several clients present ECDHE ciphers during the "Hello client" step. However, the MariaDB server never seems to negotiate the ECDHE (Elliptic Curve Diffie-Hellman) ciphers, even if there is no restriction in the ssl-cipher parameter in [mysqld].
I have the impression that something must be wrong somewhere.
By the way, wouldn't it be a better choice to make MariaDB server choose his favorite cipher ? (see SSLHonorCipherOrder parameter, available in Apache) ?