Safari has always hampered PWAs, and probably for the reason that they want you to use the appstore instead ($$$).
If PWAs are so bad on iOS and great on Android, why do companies bother with writing Android apps, web apps for computers and iOS apps instead of just telling Android users to use the web apps?
Push notifications from PWAs are another area that is unnecessarily limited on iOS. They only work if the user has added your PWA to their home screen and Safari doesn't support the install prompts available in Chrome and similar.
So your users will need to go out of their way to add the PWA to their home screen and then they can receive silent push notifications because Apple says sound and vibrations are only allowed for native apps.