[eddyg]

Worth mentioning Draw.io: https://about.draw.io which can also be run totally "offline".

The types of diagrams you can create is quite extensive: https://about.draw.io/features/examples/

and the diagrams generated are easily integrated into MediaWiki installations, with full editability.

draw.io online is a free-to-license web application for everyone. It is completely free to use for any purpose, there is no premium pay-for functionality, watermarking, or other limitations. You own the content you produce with draw.io and may use it for any purpose, including commercially. We don’t sell your personal information or data. We don’t store your data. You own your data and the application is open source.

Code here: https://github.com/jgraph/drawio