[mdpm]

https://app.diagrams.net/

Versioned, text format diagrams.

Alternately as mentioned, the mermaid DSL or similar, but this is daunting for non-technical users. I'm more a fan of having people be able to think and communicate visually, as the technical users are both the least likely to need the visuals, and if capable of creating them, the visuals are less valuable.

Mermaid is a great output format for documentation though if you're rendering these from API/code.