But unfortunately not on Safari respectively the iOS webview, which would have been mandatory for the author to use. If I am wrong, I‘d gladly take a solution. I think this is one of the main problems for PWAs: No good , platform-independent way to access the local file system. As in „pick once, access forever“.

Edit: https://caniuse.com/native-filesystem-api

Edit2: Just a few posts down: https://webamp.org/