The 2017 DC Animated Universe comic released in 2017 appeared at what Comic-Con?
DC animated universe:  Animation from the early 1990s to mid-2000s; beginning with "" in 1992, briefly ending with "Justice League Unlimited" in 2006 and returning with "Batman and Harley Quinn" in 2017. Batman and Harley Quinn:  It premiered on July 21, 2017 at San Diego Comic-Con International and was released into participating theaters for one night only on August 14, 2017.
San Diego Comic-Con International