index.ts

import ShopAPI from './ShopAPIPlugin';
import Portals from '@ionic/portals';

const App: React.FC<InitialContext> = () => {
    const [sessionInfo, setSession] = useState(null);
    const [startingRoute, setInitialRoute] = useState(null);

    useEffect(() => {
        const [context, sessionInfo] = await Promise.all([
            Portals.getInitialContext(),
            ShopAPI.getSessionInfo()
        ]);
        setInitialRoute(context.startingRoute);
        setSessionInfo(sessionInfo);
    }, []);
    
    // ...
   }
};

portal.kt

import io.ionic.portals.Portal;
import io.ionic.portals.PortalFragment;

class ProfileFragment : PortalFragment {

    override fun onViewCreated(@NotNull View view, Bundle savedInstanceState) {
        val portal: Portal = PortalBuilder("myPortal")
             .addPlugin(ShopAPIPlugin::class.java)
             .setInitialContext(mapOf("startingRoute" to "/home"))
             .setStartDir("web_app")
             .create()
        
        var portalView = PortalWebView();

        super.onViewCreated(portalView, savedInstanceState);
    }
}

portal.swift

import IonicPortals

class HomeViewController: AppParticipantViewController {

    override func viewDidLoad() {
        let portal = PortalBuilder("myPortal")
                         .setInitialContext(["startingRoute", "/home"])
                         .setStartDir("web_app")
                         .create()
          
        self.view = PortalWebView(frame: view.frame, portal: portal)
        super.viewDidLoad()
    }
    
}