What about changing sex with the use of technology and engineering?

Maybe, and if/when that day comes I am willing to consider former males who produce ova and not sperm as having changed their sex and I would see them man-made females and vice versa for former females. Worth noting that I wouldn’t consider this achieved through the organ donation of the sex organs of a deceased female/male as that would be the deceased female/male producing the ova/sperm, not the male/female using the deceased female’s/male’s sex organs.

Is there a reason why a neopenis that looks, feels, and functions exactly like natural penises can not be considered a real penis? Or a neovagina that looks, feels, and functions exactly like natural vaginas can not be considered a real vagina?

If it’s made of vagina cells, has all the functions of a vagina and is made of the person’s own genetic material (not the vagina of a deceased female) then I would consider the neovagina a real man-made vagina. As a lesbian it wouldn’t make me interested in sexually interacting with that man-made vagina though. A male in the future could perhaps with futuristic technology become a man-made female but a male could never become a natural female (a female with a female origin) as history is unchangeable. I would define attraction to man-made females as female attraction but at that stage we would probably create a new system for categorizing sexuality as many monosexuals tend to care about the origin too.

Some trans people seem to think origin shouldn’t matter in hypotheticals like these but humans tend care about origins overall. Most vegetarians wouldn’t eat man-made carrots made from genetically engineered meat of slaughtered cows, most wouldn't pay the same price for a copy of a Rembrandt painting copy as for a Rembrandt painting original, most would be more excited about a love letter written by a crush than the same letter written by someone we don’t care about it. We care about the origin/history as we care about the story behind, someone who artificially made themselves female has another story than someone who was just born that with a female body without intention. So in short I would consider a man-made female as being female, but I wouldn’t consider man-made females as the same as natural females.

At the moment no trans person is even close to having changed sex though, we hear about pregnant "trans men", but never of pregnant "trans women", we hear of "trans women" impregnating but never of "trans men" impregnating, female partners of "trans women" are told to use birth control and "trans men" are told the same if they have male partners.