Frontity is described as 'free and open source framework for building fast WordPress themes using React. In other words, it allows to build a React frontend for a headless WordPress site, which serves its data via the WordPress REST API' and is an app in the Development category. There are four alternatives to Frontity for Self-Hosted solutions, React and SaaS. The best alternative is Gatsby, which is both free and Open Source. Other great apps like Frontity are Next.js (Free, Open Source), Nuxt.js (Free, Open Source) and Gridsome (Free, Open Source).
What is Nuxt.js?: Its main scope is UI rendering while abstracting away the client/server distribution. Our goal is to create a framework flexible enough that you can use it as a main project base or in addition to your current project based on Node.js.