In ancient Rome the marriage between two males was never legally allowed, only in odd obscure cases like what Nero did, but he was an emperor and was above the law. I guess there were some people who lived in same sex unions but it was never formally a marriage. Theodosian's Codex was against it, but it was never allowed in the first place. The Roman Empire was a patriarchal society and a gay male Roman citizen would lose all respect. Same sex marriages were never legally allowed in Greece either. Homosexuality of course did exist in both cases, but it was never fully socially acceptable, at least not in the form of marriages. I mean, those two societies more or less had similar views on homosexuality as Tony Soprano lol, at least the Romans. I'm not really familiar about other examples you mentioned, so I won't comment.

It's fascinating how this LGBT rights thing has in the period of the last few decades become so important in political discussions. Before it was never even mentioned in any political context but now it has become some sort of obsession for some people on the left, 'liberals' whatever (and as a reaction it has consequently also become an obsession for the right wing). The important thing to understand is that 'gay community' as imagined by the LBGT propagandists has never existed in history. You had some people practicing homosexuality here and there but they never were part of any clearly defined community asking for their 'rights'. So why the hell would anyone give "them" a right to marry between each other? Same-sex marriage as something legally accepted and formally equal as a marriage between a man and a woman exists today in some countries because the LGBT rights movements has promoted it and provided an ideological background which makes such marriage acceptable for people who adhere to that ideology/'liberal' values (a large part of society in those countries). It can't be compared to anything in history really.

Needless to say, there have been a lot of attempts of historical revisionism on this issue, to suit the current social-ideological trends and somehow legitimize them (even though LGBT rights activists present themselves as progressive, they still look for some affirmation for their ideology in Western history, particularly in the pre-Christian era). There is also a trend to declare certain historical persons as homosexual even though there isn't much proof. Frederick II comes to my mind.