This idea that Nostr is "immutable and verifiable", as in being a single source of truth, is the biggest lie in Nostr. So many people misunderstand it. Yes, you can verify **individual events** by their signature... **if you have them**. That's a big if. Authors can delete these events at any time, and once they do, your client will also delete them from your local database. They can ship new versions of replaceable events, and that will make things disappear in your local DB too. If your Client was not active, it would have never seen some of the changes in the first place. Once that happens, you can't "verify" anything anymore.
Nostr, as a database of events, is only "immutable and verifiable" if you have a special relay that can track and store all regular and replaceable events as they happen and reject all types of deletions at all times. There is no way around it. And that relay is a **trusted** entity, since there is no way to verify if that relay hasn't deleted anything it doesn't like. Events have never been "immutable". Events by themselves are only verifiable if you have them. A chain of events is not verifiable unless you secure the storage of the entire chain by yourself in real-time. Nostr doesn't do that for you automatically.
Nostr is not a blockchain. Stop thinking it is one. It was specifically designed to NOT be one. It's not a problem to be solved.