Hacker News Reader

React Native. Why would you want a desktop app when it's already working in a browser?

If you really want a desktop app, I would recommend using React for the web, React with Electron for desktop, and React with CapacitorJS for mobile.

I want the mobile and desktop versions to be able to operate in offline mode with a local database.

You can use the React + (Browser, Capacitor, Electron) stack to do this. I'd recommend against React Native. OP's suggestion is superior IMHO.