Desktop DevTools, first-party remote debugging, injected consoles, packet capture and cross-platform WebView debugging — where each one stops, and a blank-screen case localized in about fifteen minutes.
Desktop debugging solves code problems; mobile debugging solves environment problems. Follow these four steps from Chrome emulation all the way into the app's closed WebView.
Mobile is not a browser — it is five wrapped layers: browser, WebView, system, network and performance. Take them apart in order and real-device debugging stops being a guessing game.
On the desktop, debugging means fixing code. On mobile it means fixing the environment, the code and the compatibility. Work down from desktop groundwork to real devices to the WebView.