I have this strange issue, my manually added MQTT sensors are not working in the new config, the error reads: Invalid config for [sensor]: required key not provided @ data[‘platform’]. Got None. (See /config/configuration.yaml, line 11).
Just a quick guess: With the new config you should put the mqtt sensors either in configuration.yaml directly under the mqtt: key, or in a mqtt.yaml file that you include. not in the sensors.yaml file.