@James.Morrison o me, an “iOS web app” is a web page that you open in iOS Safari and once loaded you click the little share icon and select “Add to Home screen”. Then, go and click that newly added icon on your home screen. So no native iOS or Swift.
Also, upon reading Link Button on Homescreen on iPhone does not work it seems to not be a solution. They use the page you redirected to from Auth0 as the URL to suggest to add to the Home screen. That URL will only make sense for about 2 hours then it doesn’t work any more.
As an example, if you have an iPhone try adding https://workon.app to the Home screen and the open it and click the “Authentication” link in the footer. Takes you out of the app. Always.