Apple just doesn't do it in any way. There's no way to permamently store data on Safari. At least Google Chrome has the File writer API (even though it would be good to have permament IndexedDB storage as well).

IIRC you can permanently store information under iOS Safari if the site is installed as a PWA, which makes some amount of sense. By associating long term storage with the intentional action of adding to Home Screen, sites are prevented from storing things without user permission and the feature's capability as a method of fingerprinting is greatly reduced.

Apple has gimped PWA support for iOS. It’s support and lack of features is atrocious.