Flutter is an open-source UI framework developed by Google that allows developers to create high-performance, cross-platform mobile applications with a single codebase.

Strapi is an open source headless CMS that provides a customizable content management system and API for your projects. It allows you to manage content in a visual interface and use a REST or GraphQL API to retrieve the data.

Use Stripe's software and APIs to accept payments, send payouts, and manage their businesses online.