The Eldraeverse

Boldly Coming: For much the same reasons as are covered under Bi the Way and Everyone Is Bi, there is actually quite a bit of this around.  Species becoming something close to one of those optional attributes helps too, in extreme cases, as do virtual sex and the ability to remap sensoria appropriately.

But, essentially, given the general attitudes that “minds matter, bodies much less so” and “speciesism is something that, well, only the most insanely backward primitives indulge in”, well, yes, of course you’re going to get a fair old bit of xenosexuality.  Even if you have to pay a lot more attention to the logistics and medical issues than Captain Kirk ever did.