List of global ethnicities Looking at the 1000 genomes project I see the following list of population groups and super-groups:
https://www.internationalgenome.org/category/population/

However, is there something like a standard list of global ethnicity? Like an ontology of population diversity or similar?

I'm trying to tie genome data to 'ancestry', and to do that I'd like to survey a set of people on their ancestral background (as far back as grandparents ideally).

How to capture diversity in terms of what people 'self report' in their backgrounds? e.g. middle / far east, north / south India, etc.
It's not clear exactly what your goal is. It might help to have an idea of how you are trying to use this data; and it's probably not a bioinformatics question, as ethnicities are social/political rather than biological constructs.

However, there exist some controlled vocabularies used by LoC for ethnic groups; that looks a bit old so it might not be the best source.

I am by no means an anthropologist but it does look like there are anthropological databases devoted to e.g. ethnography that may have complementary information.

Wikipedia has a simple list of ethnicities that notes, instructively, "There has been constant debate over the classification of ethnic groups."

I think that you are unlikely to find a single authoritative answer that is safe to use as a source of truth. I would normally suggest to try another stackexchange site, though it looks like there is none for sociology or anthropology. There is no anthropology tag available on this site, but you might try posting in e.g. history.stackexchange.com and adding an anthro tag.