WP2Static - Static site generator for WordPress
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
GatsbyJS - Blazing-fast static site generator for React
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.
Hugo - Hugo is a general-purpose website framework for generating static web pages.
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.