Well, as far as I know, usually there isn't a built-in feature to notify you when someone takes a screenshot of your story. But some social media or apps might have third-party extensions or tools that claim to do this, but their reliability can be questionable.
Honestly, there's no definite way to know for sure when someone screenshots your story. It's kind of a mystery. Some platforms might give hints or rumors about possible methods, but they're often not accurate or reliable.