Apple has released iOS 12.1.2 for iPhone and iPad bringing a minor patch designed to fix problems with eSIM support on the iPhone XR, XS, and XS Max, as well as cellular connectivity with the same phones in Turkey.
The update is available through iTunes, or as an over-the-air update in the iOS Settings app.
With iOS 12.1, iPhone XS, iPhone XS Max and iPhone XR gained Dual SIM support, featuring a nano-SIM and digital eSIM. Users can now activate an additional cellular plan from a carrier without having to use a physical nano-SIM.
In most regions the second SIM is actually an eSIM, though with Chinese iPhones, users must use a second physical card.