If I may, I would recommend to emphasize that rendering is done via an external service, meaning that the diagram code gets transmitted to a third party.

Fabian Iwand

Fair point. If you have suggestions for alternative rendering approaches, would love to see them.

Unfortunately I don't (aside from switching to other solutions like Mermaid), and there don't seem to be any renderers written in other languages that could be compiled to JS or wasm.

I think it should suffice to add "via the PlantUML web service" to this notebook's first sentence.