"Add to Home Screen" saves wrong URL
The way that iOS apps save/install to the homescreen is by checking something called the manifest. (see more)

The URL being referenced in the manifest.json at the specified URL is pointing to "/" meaning the root of the site which means it is working as expected.


There are two options to resolving it


Change the start_URL to match your destination i.e. "/covid19app/home" instead of "/"
Look into options to creating a relative URL per page based on the header URL if needed for multiple pages.


Your manifest.json file is located in the root directory. Alternately you can find resources to creating one for a web app.