How should I start building a camera and group-chat mobile app?

Since you already know web development, React Native with Expo could be a comfortable starting point. Begin with a very small prototype: take a photo, save or upload it, add basic authentication, and then build a simple group chat. Leave widgets and notifications until the main app works, because those features often require extra Android- and iOS-specific code. For the backend, Firebase or Supabase can provide authentication, storage, a database, and real-time updates without requiring you to build everything yourself.

Capacitor is another option if you want to keep using your existing web-development skills. It packages a web app as a mobile application and provides access to native features through plugins. Camera support may require some extra configuration, and you’ll still need to test carefully on both Android and iOS.

A web-based approach or WebView could work for a basic prototype if the app is not performance-intensive. However, camera access, push notifications, and home-screen widgets can be awkward in a WebView, so a cross-platform framework with native integrations will likely be easier as the project becomes more advanced.