Should I use React Native?

A friend of mine looking to start a company has asked me to help him on the tech side.

He is in the process of raising seed funding and comes from a non-technical background. He is building an app that will need to be available across web, iOS, and Android. How should he go about building the app?

I’m a full stack freelance developer with a focus on Javascript. I mostly React for the frontend work I do. I also run a popular fantasy football game. The mobile apps for this game are written in React Native (both Android and iOS).