https://www.theverge.com/circuitbreaker/2018/10/30/18042266/verizon-apple-dual-sim-esim-setup-issues-2g-cdma

iOS 12.1 is set to roll out today and bring a variety of useful improvements, including dual-SIM support for iPhone XS and XR — but if you’re a Verizon customer, that two-line system might not work very well, at least for now, according to a report from PC Mag.

The issue is how the new iPhones handle having two SIM cards: unless you live in China (where Apple is selling a special XR model for two physical SIM cards), the XS and XR will support the two lines of service through a combination of the regular, physical SIM and a digital eSIM.