The 2-year-old Samsung Galaxy S6 line is finally receiving Android Nougat, at least on AT&T. The devices are being upgraded to version 7.0 and should enjoy all of Nougat's software improvements and new features.
http://www.notebookcheck.net/Android-Nougat-upgrade-is-rolling-out-to-AT-T-s-Galaxy-S6-devices.217454.0.html