Excalidraw is quickly becoming my main tool for illustrating quick concepts and creating wire frames. it's super fast and lightweight. give it a spin. https://excalidraw.com . Its open source and you can just run it on localhost.
The fact that it opens straight into create mode instead of having you go through file management is amazing for one-off use cases
there's even a plugin available on Obsidian for note takers with a visual preference
And the Code extension is incredible. Name a file as .excalidraw or .excalidraw.svg and you have an excalidraw editor in vs code, that saves as an svg and works with git. https://marketplace.visualstudio.com/items?itemName=pomdtr.excalidraw-editor