It’s an annoying workaround, but could he connect a USB keyboard (via a USB to lightning adapter) with the ability to enter the character? Does the passcode screen accept input from attached keyboards?
It's mentioned in the article. USB devices are blocked until the passcode has been entered.
As mentioned in the article,
> For the same reason, plugging in an external keyboard is also a no-go since freshly updated iPhones are placed in what's known as a Before First Unlock state, which prevents wired accessories from working until the passcode is entered.