Uxn will use any available mouse device, it doesn't handle tablets any differently.
Have you had issues with other SDL applications in the past?
not that i know of but i didn't find any signs of Excalidraw, Krita or Clip Studio using SDL, so i'm open to test my tablet on anything on it you're point me to as interesting and or suitable for such test
had zero issues with Blender, they seem to use SDL:
https://developer.blender.org/diffusion/B/browse/master/?grep=SDL