sexuality - To what extent is homosexuality forbidden among non-Jews?

All homosexual behavior is forbidden among Jews, but some actions are clearly Torah prohibitions (e.g. mishkav zachar), while some might be Rabbinic in nature (e.g. lesbian relations). Are all of these forbidden for non-Jews, or may non-Jews perform some behaviors that are Rabbinically prohibited to Jews?

Here are my thoughts: On the one hand, I would have thought that Rabbinic prohibitions should not apply to non-Jews at all. On the other hand, the very fact that lesbian relations are looked down upon as maaseh Mitzrayim ("the way of the Egyptians") would seem to imply that it is bad for non-Jews to perform them as well.

In addition, for some homosexual relations there is an argument among the Rishonim about whether they are Torah or Rabbinic prohibitions (e.g. forms of male intimacy that fall under the prohibition of lo tikrevu). We hold by those who say that they are prohibited by the Torah, but I wonder whether non-Jews might be able to rely on those who say that they are only Rabbinically prohibited for Jews, and therefore possibly permitted to non-Jews.