Recommendations for the iPhone Duo release.

If you are asking whether the iPhone Duo supports physical SIM cards, I believe the answer is No. The Technical Specifications for the U.S. model say that it

• [Supports] Dual eSIM (two active eSIMs; stores eight or more eSIMs)
• iPhone Duo uses advanced eSIM technology for more convenience and security (not compatible with physical SIM cards).

Other sources – including AT&T – indicate that the iPhone Duo is eSIM-only worldwide.

AT&T – The new Apple iPhone Duo is coming

"Is the iPhone Duo eSIM-only?

Yes. The iPhone Duo is eSIM-only worldwide, with no physical SIM card slot in any country. This design choice saves internal space for the hinge and battery components."

MobiSim – Does iPhone Duo Support eSIM? Everything You Need to Know

"Unlike many previous iPhone generations, where the presence of a physical SIM slot depended on the country in which the device was sold, the iPhone Duo is eSIM-only worldwide. There is no physical SIM card slot."