Thanks for proposing this change. It doesn't look like bitnami has a secure kafka image offered in their new bitnamisecure so this looks like the right path forward to use the official Apache release.

I've got two main points of feedback, with the second being critical for ensuring the sample works as intended.

Image Transition & Configuration
I totally understand the Kafka setup is secondary to the Dataflow portion, but I'm wondering how much you've confirmed changes based on swapping out a "polished" image (Bitnami) for an "upstream" one (Apache):

Documentation Context: Could you please add a brief note to the README explaining why we are moving from bitnami/kafka to apache/kafka? This helps future contributors (including sample reviewers) and users understand the dependency choice.

Default Configuration: The Bitnami image often included built-in security defaults and environment variables. Have you confirmed that the basic apache/kafka image provides a drop-in functional equivalent for this simple setup, or if any additional variables are needed to maintain security/stability? We might want to add a note at the top around this sample showcasing how to do this for local development and not showing production-quality kafka configuration.

I believe that apache/kafka:latest currently points to the 4.x.x stream https://hub.docker.com/r/apache/kafka which runs Kafka without ZooKeeper. The tutorial documentation still contains steps and infrastructure setup (firewall rule for port 2181) that assume a ZooKeeper-based Kafka instance (which the original bitnami/kafka:3.4.0 was).If we use $4.x$ while retaining the ZooKeeper setup instructions, the commands in the "Sending messages to Kafka server" section will likely fail, blocking the user from running the Dataflow pipeline.

I think this means either refactoring the instructions or pin the image to a specific, recent $3.x.x$ version that is confirmed to be ZooKeeper-compatible and serves as a direct functional replacement. In general, it's better to pin to a specific version in samples to ensure that users can replicate a known good experience.