Doing some research for a work-related task, I needed to learn the basics of Kafka, so I tried a visual approach instead of just reading some tutorials or a book (which takes more than a few hours). Learn Apache Kafka for Beginners is an introductory course that lasts between 3 and 4 hours, depending on if you use Java, Scala, Akka or similar or not, as you will skip the corresponding videos demoing basic consumer-producer examples.
You will learn the basics of Kafka: How it works, producers, consumers, topics, partitions, offsets, segments, basic setup and configuration (including a handy Docker small cluster for local development), and some tips and advices regarding how to properly configure everything. Considering that it also has coding demos, while a small course the content is fine and very well summarized and presented.
There are other more advanced courses (which I'll probably take), regarding Streams, Connectors and other non-trivial areas.
An insightful introduction, recommended.