Quark did think that the female Ferengi that was passing as a man was making a move on him, at least right before he found out the truth. I think any species that has gender will have homosexuality. That seems to be the way it works in Trek from what we've seen. At the very least in the novels when gay and alternative orientations among aliens are seen, there doesn't seem to be any surprise. It's presented as being completely natural, and in the novels there have been gay Trills, Klingons, Vulcans, humans of course, and an Andorian who is not attracted to three different genders would be the minority.
Are there any other alien races we've seen gay members of that I didn't mention?
If Q could even be said to have gender and an orientation I think he'd be a bisexual male.