Can you share more details about what you're trying to accomplish?
There aren't that many options:
- You want to embed discussion features in an app
- Use webview
- Create native frontend interacting with Flarum API
- You want to integrate Flarum login and other custom features, but not discussions
- Create feature as a full Flarum extension, and embed with webview
- Create only the API side of the feature in Flarum, and implement the user interface in the app
- Create custom login interface that interacts with the Flarum API to login, then use the token to interact using the REST API
If you're not going to use webviews, you will probably have a lot of work re-implementing every single feature of the Flarum frontend. You'll also have additional work for each community extension you want to use.