Shoutem is an easy-to-use mobile app builder for Android and iOS. It comes with a Drag and Drop interface, a range of extensions, themes, a UI toolkit, 200+ customizable layouts, and more.
Shoutem is completely free and open-sourced for developers. Use an unlimited number of extensions in your app. There are some premium features, like automated publishing to both stores. See the pricing details here.
If you are not a developer, you can use one of the paid plans and try it for a 14-day free trial. No credit card required. After that, prices start at $59 per month when billed annually.