Framer Preview is described as 'is the best way to view and interact with your prototypes on an iOS or Android device'. There are five alternatives to Framer Preview for a variety of platforms, including iPhone, iPad, Android, Android Tablet and Sketch. The best alternative is Lunacy, which is free. Other great apps like Framer Preview are Figma Mirror (Free), Design Mirror (Paid), Adobe XD Mirror (Free Personal) and Sketch Mirror (Free).
Lunacy is a native Windows app that opens, edits, and stores .sketch files. In short, it’s long-awaited Sketch for Windows. It solves the big pain of design teams working on different operating systems and improves the process of transition from design to development.