I don't have all the details but I believe that the native population (the Kanak) managed to get an agreement a few decades ago to make sure only they could vote in their local elections. This was done and seen as an anti-colonial move.
Recently the French government, without a care in the world or of its word, decided to revert this agreement without actually consulting the ones mostly impacted by it, i.e. the Kanak, and allow residents to vote as well (you would need a 10 years residence in New Caledonia to be able to vote)
I believe there was a referendum about voting rights and independence but abstention was really high so the results are not very representative, and given that France doesn't give abstention/null voting any value, the government chose to ignore the population's actual feelings and do its own thing.
It's a pretty interesting move given the current context and the support France has given to Israel.