I love #Inkscape, and I love giving talks! So why not make slides using Inkscape?
My idea is to write a tool that looks at the layers of an SVG document, and creates one PDF page per layer, in top-to-bottom order. On the page, only that layer, plus all parent layers, would be visible.
That way, you could have an always-visible "master slide" in the background, and create simple step-by-step animations. In this example, "2" would be shown first, then "2a", then "2ab". After that, only "3".
This is clearly inspired by #JessyInk, an #Inkscape plugin that does a similar thing! I've used it to give talks in the past. It's pretty neat, and even though it hasn't been updated since ~2010, it still works!
But it doesn't support nested layers/step-by-step animations, and the only way to view the result is to open a JavaScript-instrumented SVG in the browser…