Hi, is dual sim card iphone available at Apple online store?

eSIM on iPhone is not offered in China mainland. In Hong Kong and Macao, iPhone 12 mini, iPhone SE (2nd generation), and iPhone XS feature eSIM. Learn about using Dual SIM with two nano-SIM cards in China mainland, Hong Kong, and Macao.

No, the US models will not be Dual SIM slot. As stated above, it will have one eSIM and one Nano sim slot.