Is this supposedly ancient Greek vase painting real?

Probably. Don't know about this one, but there's a lot ancient Greek porn-y artwork that's like this. I've seen them in person.

r1 I know that there's and I more-or-less collect the gay ones. But it's weird that Google has only one result.

No, silly. It was made in the 1990s.

the real sex scenes depicted are hot, but not as clearly designed.

More real Greek actives:

First, if it's real, it's a modern drawing of the vase painting, not a photograph. I'm not an art historian, but I'm suspecting it's a modern improvisation on red-figure orgy scenes (which are a real thing, but so are modern imitations). The choking looks like a modern element, and some of the sexual positions look more like modern porn staples. The little guy fucking the big guy seems unlikely except in a comical situation. The combination of men in helmets and greaves and men fully naked looks inauthentic, as does the lack of variety among the participants (basically two types, except for height). I'm missing situational details in such an extensive scene (e.g. little pieces of furniture, tokens of a symposiastic setting or similar, slight differences in the characters' dress and hair, etc.).

getting ready to ride it!

Here's a clue: in authentic Greek gay porn, the tops always have beards and the bottoms are always clean-shaven. That's the way it was back then, when tops were tops and bottoms were bottoms (i.e., no one was versatile).

Also, very few such vases remain, because nasty fanatical early Christians smashed so many of them. Dumb shits.

r7 But in the figure in the OP, the top is wearing a helmet. You can't tell if he has a beard or not.

No doubt early Christians objected to sexual scenes in art, but the main reason sexy vase paintings are found broken is why vase paintings of any subjects are found that way—because they couldn't survive over 2500 years—not specifically because of Christian hostility. And sexy vase paintings aren't "very few," they represent a pretty healthy of the corpus of Athenian red-figure (or black-figure, as in R3) that we have.

healthy *cross-section*

It looks completely modern, and computer-generated.

There's a clue bottom right in the Greek key pattern: 02 18.

More Reverse-Googlage reveals it's quite possibly a painting by Dmitry Bitjukov, a painter and erotic illustrator based in Riga, Latvia.

Upbringing of youth 500 x 900 mm February 2018 Acrylic paints on canvas

I personally think it was inspired by Armand and Albert's china pattern ;).

Btw, the illustration in R6 is of a guy and a girl. She has a hairdo like that of sex workers (for want of a better term) in other contemporary Athenian vase paintings, and you can see a little boobage.