The Legend of Korra, the sequel to Avatar: The Last Airbender, made history in 2014 in the episode "The Last Stand", which is the 13th and final episode of Book Four: Balance. At the very end of this episode, Avatar Korra and Asami Sato take a trip hand-in-hand to the Spirit Realm. It was confirmed shortly after by Avatar: Legends creators Bryan Konietzko and Michael Dante DiMartino that Korra and Asami are both bisexual and in a romantic relationship (funny enough, they dated the same guy, both at different times, but that makes it one of the few "true" love triangles). They later kiss in the follow-up comics, where it is also revealed that Avatar Aang's daughter Kya is a lesbian, and Avatar Kyoshi was openly bisexual.
https://www.youtube.com/watch?v=RwN340U5-4M
Are there any other modern ships that changed history?