I haven't looked at this lately and so don't have a specific recommendation, but there are small libraries for helping iOS learn how to add PWAs using the standard Share → Add to Home Screen mechanism.
I've seen guides like this before. Would be nice if they showed what the share button looks like, cause that's not obvious to some people. Or, some file sharing websites show an arrow pointing to the downloads button in desktop Safari.
https://github.com/khmyznikov/pwa-install (Try on device: https://khmyznikov.com/pwa-install/)