Most ancient Western cultures had really rigid gender roles, even the ones were same sex relationships were accepted. For a lot of those groups, like the Romans, Greeks, and Celts, gay sex was considered part of how soldiers bonded, and it was typically intercrural (non penetrative.) A lot of cultures that accepted gay relationships still considered being penetrated to be feminine and humiliating, hence the intercrural sex.
Pre-Christian Norse had really rigid gender roles, to the point where men and women had separate "heavens." They believed that women were uniquely capable of practicing magic (traveling Norse medicine women, called völva, are the origin of the "witch" myth.) While he wouldn't be burned at the stake for it, any man who engaged in "feminine" behavior like magic (or bottoming) would be considered the village idiot. A guy receiving anal was a faux-pas, but being romantically involved with the same sex wasn't. Basically, you could be gay, but you couldn't be feminine, so if troons existed in Norway in the middle ages, they would still be considered freaks and social outcasts.