-   So is tldrawDigital whiteboard with infinite canvas ★ 43.5K Diagram License: MITTldraw is a library for creating infinite canvas experiences in React. It's the software behind the digital whiteboard tldraw.com. 
-   So is ExcalidrawLavagna per disegnare schemi come fatti a mano ★ 109.2K Diagram Whiteboard License: MITUna lavagna virtuale open source in stile disegnato a mano. Collaborativa e crittografata end-to-end.  
-   So is Draw.ioJavaScript, client-side editor for general diagramming ★ 57.5K Diagram License: Apache-2.0Browser-based diagramming components and applications.  
-   So is D2Turn text into diagrams ★ 22.3K Diagram License: MPL-2.0A modern diagram scripting language that turns text to diagrams. 
-   So is Mermaid Live EditorModifica, visualizza in anteprima e condividi diagrammi/grafici mermaid ★ 5.6K Diagram License: MITModifica, anteprima e condivisione di diagrammi/grafici mermaid.  
Sure, Lucidchart is awesome.
But have you considered these open source alternatives?
They are free, self-hostable and community-driven.
Check by yourself: tldraw , Excalidraw , Draw.io , D2 , Mermaid Live Editor .