Sure, Visio is awesome.

But have you considered these open source alternatives?

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

Check by yourself: Excalidraw  Excalidraw , diagrams.net  Draw.io .

  1. So is Excalidraw Excalidraw

    Whiteboard for sketching hand-drawn like diagrams

    ★ 93.7K Diagram Whiteboard License: MIT

    An open source virtual hand-drawn style whiteboard. Collaborative and end-to-end encrypted.

    preview

  2. So is diagrams.net Draw.io

    JavaScript, client-side editor for general diagramming

    ★ 52.8K Diagram License: Apache-2.0

    Browser-based diagramming components and applications.

    preview