Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Atomize by Quarkly - Library for creating atomic react components
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
Ant Design - An enterprise-class UI design language and React implementation with a set of high-quality React components, one of best React UI library for enterprises
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.
Material UI - A CSS Framework and a Set of React Components that Implement Google's Material Design