AT&T becomes the first U.S. carrier to offer iPhone eSIM support
Now, Verizon and T-Mobile have already committed to bringing eSIM support in the coming months, but it looks like AT&T is the first to offer the new feature to iPhone users. Although no official announcements have been made, AT&T's support page details eSIM support and how you can have two SIMs active in your iPhone XS, XS Max or XR.
If you own one of the three iPhone models, simply go to Settings / Cellular / Add a plan, and when the Camera app opens point it at the QR activation code on your eSIM card until you see a message that says “Installing cellular plan.”
Rumor has it that T-Mobile is expected to introduce eSIM support for iPhones by the end of the year, while Verizon should debut the new feature early next year. Sprint is going to add eSIM support as well, but an ETA hasn't been announced yet.