Sure, Lucidchart is awesome.

But have you considered these open source alternatives?

They are free, self-hostable and community-driven.

Check by yourself: D2 , Excalidraw , tldraw , Draw.io , Mermaid Live Editor .

So is D2

Turn text into diagrams
★ 25K Diagram License: MPL-2.0
A modern diagram scripting language that turns text to diagrams.

Read more about D2
So is Excalidraw

Whiteboard for sketching hand-drawn like diagrams
★ 130K Diagram Whiteboard License: MIT
An open source virtual hand-drawn style whiteboard. Collaborative and end-to-end encrypted.

Read more about Excalidraw
So is tldraw

Digital whiteboard with infinite canvas
★ 49.9K Diagram License: MIT
Tldraw is a library for creating infinite canvas experiences in React. It's the software behind the digital whiteboard tldraw.com.

Read more about tldraw
So is Draw.io

JavaScript, client-side editor for general diagramming
★ 62.7K Diagram License: Apache-2.0
Browser-based diagramming components and applications.

Read more about Draw.io
So is Mermaid Live Editor

Edit, preview and share mermaid charts/diagrams
★ 6.8K Diagram License: MIT
Edit, preview and share mermaid charts/diagrams.

Read more about Mermaid Live Editor