Eclipse Ditto can either consume messages directly from an MQTT broker using MQTT 3.1.1 or MQTT 5:
Or, utilising Eclipse Hono as device connectivity layer, consume messages via Apache Kafka or AMQP 1.0 (which Hono uses for "northbound" applications ingesting telemetry data).
If you need Eclipse Hono, I suggest to have a look at the "Cloud 2 Edge" package in the Eclipse IoT Packages project which already automatically sets up and configures both Eclipse Hono and Eclipse Ditto to work with each other:
If you only need to send data via MQTT, I would suggest to use an MQTT broker (like Eclipse Mosquitto) as this simplifies the setup a lot.
If you have requirements towards supporting multiple IoT protocols or massive scalability requirements, Eclipse Hono is a good choice.