Sure, Lucidchart is awesome.

But have you considered these open source alternatives?

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

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

So is Excalidraw

Lavagna per disegnare schemi come fatti a mano
★ 130K Diagram Whiteboard License: MIT
Una lavagna virtuale open source in stile disegnato a mano. Collaborativa e crittografata end-to-end.

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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 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.

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So is Mermaid Live Editor

Modifica, visualizza in anteprima e condividi diagrammi/grafici mermaid
★ 6.8K Diagram License: MIT
Modifica, anteprima e condivisione di diagrammi/grafici mermaid.

Read more about Mermaid Live Editor