I wouldn't say Affinity Designer is a workaround and it's far more capable and powerful (and less painful to use) than PowerPoint for UI design. But...you can

I wouldn't say Affinity Designer is a workaround and it's far more capable and powerful (and less painful to use) than PowerPoint for UI design. But...you can use PowerPoint or Keynote for creating simple clickable prototypes that can be very effective. For example: https://keynotopia.com/ https://keynotopia.com/