This repository is an example of a React Native app (running on Expo to show how to render an OpenCerts file using a webview.
Download the Expo Client for your ios/android phone at https://expo.io/tools.
The application simply open the frameless url in a webview and sebsequently injects a javascript script to set the input field in that page to the content of the certificate.
Both this application and the frameless page do not check for the validity of the certificate. The application needs to conduct the 4 step check (according to OpenCerts documentation) prior to displaying the webview.