How to activate the Kafka log in Lagom 1.6

In Lagom documentation: https://www.lagomframework.com/documentation/1.6.x/scala/KafkaServer.html

it says that the logs can be found in <your-project-root>/target/lagom-dynamic-projects/lagom-internal-meta-project-kafka/target/log4j_output

I don’t have the ‘log4j_output’ folder. Why ? What should I do to have Kafka logs ?