I am trying to set up a kafka cluster on the Openshift platform using this guide: https://developers.redhat.com/blog/2018/10/29/how-to-run-kafka-on-openshift-the-enterprise-kube
The access through routes is possible via TLS only using the CA certificate generated by Strimzi that you have to extract as described in the article. Then you have to create a key store importing the certificate and providing that to the client application. I don't see such configuration in your producer.