With the almost limitless number of Android devices on the market, the amount supporting WiFi Calling on AT&T is somewhat limited. The first Android device that AT&T allowed into the WiFi calling club was the LG G4, even after the LG G5 had been available on the network for some time.
Aside from the G4, the only other supported devices were various iPhone models, a few recent Samsung flagships, and two other LG phones. Now the LG V10 is joining that list, with a software update pushing out to owners with the new feature.
The update, with a build number of MRA58K, apparently only includes the addition of WiFi calling; sorry if you got your hopes up for a Nougat update. The download clocks in at about 368MB. If you have not received the update, you can check from the Update Center on your V10's About Phone settings menu.