To be fair, QQQ is not really an index fund. Unless you think that I can make up whatever arbitrary list of stocks I feel like, and call it an index, and create an ETF that tracks it, and still call that an index fund.

Vanguard is probably the most principled when it comes to passive index tracking, and they do not have an ETF that tracks the NASDAQ 100 (or any fund that focuses on a single stock exchange for some inexplicable reason).