you're misunderstanding: this isn't specific to passkeys, this is for changing the password manager(s) used when filling passwords, 2fa codes and passkeys.

since the person I responded to couldn't find it, I linked tutorials. it amounts to opening the Settings app, going to "General" and then "AutoFill & Passwords", so it's also not terribly difficult to find compared to other iOS settings.

you could've at least tried to understand what's being talked about before blindly complaining.