I will never accept nor in any way accommodate any other than Biblical marriage by Genesis II:24, in which the pronoun’s tense is singular.
"What established religion, if any, provides for formal same-sex marriage?"
To exclude some group of homos that have banded together out of convenience:
"Established religion" is intended to mean one that has an established, well recognized and consistent form that has been in existence for some meaningful length of time.
"Formal" is intended to mean marriage of the sort traditionally practiced by almost universally by the vast majority of cultures. To distinguish from simply acquiescing to homo engagements and forms of polygamy.