I've created a handful of PlantUML procedures to create C4-style diagrams that retain a certain amount of UML representation.
C4 doesn't recommend a standard diagrammatic style (even though Brown almost-universally uses a set of blue and grey boxes with arrows), and I still have a fondness for UML, so that's what I tend to model in. But all of Brown's recommendations about titles, labels, descriptions, and icons are great recommendations: the procedures just make it easier to lay that stuff out.
Obviously, if you prefer Brown's style, you should probably look in to the PlantUML-bundled C4 Standard Library. It's probably also more complete than this library will ever be.
The System Context Diagram doesn't really map neatly to any particular UML-style diagram (except, perhaps, as a simplified version of a UML Deployment Diagram). Because of the simplified nature, systems are represented as basic rectangles.
I have a bit of a love/hate relationship with the C4 notion of "containers." First up, the name "container" has been so completely staked out by Docker, that C4's container language is always going to have to do extra work to get the listener to understand that C4 containers have nothing to do with Docker.
Instead, I prefer to think in terms of UML artifacts. While Brown is very clear that he doesn't think that there's a 1-to-1 relationship between artifacts and containers, the distinctions aren't so great that you can't do a bit of substitution.
In my opinion, the deployment diagram is the most useful type of diagram in UML; it's also a supplementary type of diagram for the C4 model.
Deployment Diagrams show the relationship between containers (artifacts) and the infrastructure elements.
