Do you trust the banking app installed from Aurora enough to do your online banking? I don't, and I really wish there would be a decent way to verify that the installed/provided apps are legit. For me this is the biggest downside of using GrapheneOS, which I'm otherwise extremely happy with.
(for me, the whole point of using GrapheneOS is privacy and not sending data to Google, so using the PlayStore is not an option)
Android apps are signed. Can't you verify the signature?