As this answers are obsolete for latest iOS and Safari versions, does have anyone conducted a tests or investigation of how it is now?
As stated here, the "Storage Management: Persistent" should be supported from version 15.2.
Does it mean the eviction policy (7+ days of unused) would not hit data stored with flag persistent?
PWA are not affected by the 7days of unused rule. I have no issue storing datas in Indexeddb for months in my PWA, both on iOS and Android.