Excalidraw looks like a nice alternative to draw.io – it has fewer features but is faster and easier to use for quick diagrams.
- open source
- runs as a PWA (without a server)
- stores files locally
- appears to be an infinite canvas
- nice library and extensive 3rd party contributed libraries
- has a paid plus version with more features (collaboration, server features, etc)
So while Excalidraw appears to be good for quick sketches, it appears less useful for creating presentations, as I’ve done before with Draw.io. However, maybe you could create a presentation as an infinite canvas and just drag the canvas around during your presentation.
Below is an example of several diagrams I redrew from the TMPDIR handbook: