Seems like quit a bit has changed in two years since this post was made. I wanted to give an update.
Currently, these projects going on...
React Native Windows - React Native support for Microsoft's Universal Windows Platform (UWP) and the Windows Presentation Foundation (WPF)
React Native DOM - An experimental, comprehensive port of React Native to the web. (Not to be confused with React Native Web, which has different goals)
React Native Turbolinks - React Native adapter for building hybrid apps with Turbolinks 5.
React Native Desktop - A project aiming to bring React Native to the Desktop with Qt's QML. A fork of React Native Ubuntu, which is no longer maintained.
React Native macOS - An experimental React Native fork targeting macOS and Cocoa
React Native tvOS - adaptation of React Native for Apple tvOS
alita - An experimental, comprehensive port of React Native to mini-program(微信小程序).
Proton Native - A wrapper for React Native, using Qt to target Linux, MacOS, and Windows.
All of this directly from the React Native website:
https://reactnative.dev/docs/out-of-tree-platforms#docsNav