Personally terms like ethnicity, ancestry, peoples all seem much more like they have potential to be connected to ideas like blood and soil, than the way race is meant to be used in D&D (which as Celebrim pointed out, humans are all one race, drwarves and elves another, effectively different species, maybe distantly related to humans. I'm Jewish, Italian and Irish, someone having Jewish ancestry is certainly something that that has manifested in real world racism towards them. And all three of those, at least here in Boston, have cultural things associated with (things I experience when I visit different sides of the family). That concept of ethnicity or ancestry is different from the idea that all humans belong to one category: the human race (which is how D&D means it: like I said the one time I saw modifiers for different human groups in a D&D book, I found it pretty off-putting for that reason). The demihuman groups aren't really meant to be stand ins for human cultural or ethnic groups (we just draw on those and blend them to produce something new and interesting, or as shorthand: i.e. Dwarven vikings are an easy thing to grasp without much further explanation---but it isn't a commentary on viking culture, nor is it a lesson in it). To me, since there seems to be a lot of confusion around what race means in this context, species appears to be the closest thing to capturing its original meaning in the game. I would say Type could also work but that might lack flavor for people. At least that is how I have always viewed it.