You can do Add To Home, but you’ll get errors if you try to launch without any network. Though the PWA model can provide for a fully offline experience, I’ve found that only a minority offer good offline + sync. It is sort of the opposite of native apps, which usually have offline/local, and might have sync.

Usually there’s a button called “Add to Home Screen” in the dropdown menu of your mobile browser. Can you try that?

on ios you need to hit the share button and then choose the “add to home screen” option