MarkShow is described as 'Create presentations in your browser using Markdown' and is a presentation maker in the office & productivity category. There are more than 10 alternatives to MarkShow, not only websites but also apps for a variety of platforms, including Mac, Self-Hosted solutions, Windows and Linux. The best alternative is LibreOffice - Impress, which is both free and Open Source. Other great sites and apps similar to MarkShow are Google Slides, Sozi, Keynote and Marp.
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.