Slidify is described as 'Generate reproducible HTML5 slides from R markdown' and is a Presentation Maker in the Office & Productivity category. There are more than 10 alternatives to Slidify for a variety of platforms, including Online / Web-based, Mac, Self-Hosted solutions, Windows and Linux. The best alternative is LibreOffice - Impress, which is both free and Open Source. Other great apps like Slidify are Google Slides (Free), Sozi (Free, Open Source), Keynote (Free) and Marp (Free, Open Source).
We are Ludus, making a slides builder for creatives. We are mixing pro features from Sketch, with the power of internet (Sketchfab, Framer, CodePen ... are some of our integrations). So slides can be truly creative and limitless.