I personally doubt the narrative that Neantherdals were of a different species. If they were, it’s unlikely that genetic material could be exchanged.
With proper clothes and presentation, they probably weren’t that inattractive for the time they lived in.
It was a few years back in Louisville Kentucky. I met a family of Russian-Jewish immigrants. They had an attractive daughter in her early 20s but the entire family I swear to God had a lot of the physical attributes one thinks of as Neanderthal; the brow ridges, big noses, weak chins and stocky builds. I remember thinking at the time, 20 years ago, there must be an isolated village in Russia where Neanderthal survived.
Even with all these traits they were not unintelligent or unattractive. As a matter of fact I found the daughter very attractive.
Neanderthals are not a different species.
They are Homo Sapiens Neanderthalensis as compared to our Homo Sapiens Sapiens.
We are of the same species, different family, so there is no reason why they couldn’t interbreed.