I've created a Python DSL for authoring C4 models following Structurizr's schema. This means it is compatible with any Structurizr-compatible rendering tool. That said, buildzr also support exporting to C4 PlantUML and SVG out of the box.

If you've tried Structurizr DSL but finds some features wanting (like module imports, predicate based styling, static typing, ease of applying icons/themes to the C4 elements) this tool might prove useful.

Thanks, and appreciate any feedback!