According to scripture Judaism doesn't support gay marriage. Christianity is similar. Hindiusm talks about people born with out gender parts and therefore being 3rd gender but doesn't accept homosexuality. Buddhism says nothing about gay marriage or 3rd genders. Islam also is against homosexuality.
I would like to refrain from talking about intersex people (people born without sexual organs or both male and female organs), because these are incredibly rare compared to actual homosexuality, and, as outlined in Hinduism, are considered to be an exception. Chinese religions like Taoism and Confucianism say nothing about homosexuality.
Are there any religions that are both established (implying that they are relatively old, but still practiced) and explicitly support homosexuality?