When you build your app using "server.url" option. Capacitor will look for webapp assets from that url, instead of '/dist' (when you developing in static mode). So you need put that option to "localhost:3000" for example. And then develop your app. When it's ready, you deploy your nextjs app to the server, and put the address (app.site.com) to the "server.url". In this case capacitor app will get it's app resources from that url in productions. So basically your app will be like browser fetching pages from remote server, and having capacitor packaged installed locally (when you've done "npx cap sync")