>xenomorph in a high fantasy setting and still get a sense of fear
I wouldn't really call a xenomorph Lovecraftian, but there's actually multiple examples of xenomorph-like creatures, with the closest probably being the kythons .
As far as Lovecraftian horrors, those have been touched upon in each edition of D&D, often with the denizens of the Far Realms acting as powerful but very alien creatures. There's even a book called Elder Evils that explains how to work other kinds of Lovecraftian Superhorrors into campaigns, from low level adventurers investigating cultists to epic level adventurers hoping to figure out some way of stopping the Elder Evils directly.
As for the sense of fear, that's done easily enough. Even in an ordinary campaign you can terrify players with strong monsters, force them to question their sanity by experiencing hallucinations and visions, or fill them with dread that something beyond their understanding is coming to kill them all.
The line between science-fiction and fantasy tends to blur quite a bit, and you can see the influences of one in the other quite often, since there are many overlapping themes and concepts. For example, Dagon of Lovecraft fame finds himself as a demon lord in D&D.