Index fund is the basis of the market situation right?
I think in cryptocurrency, Bitcoin is the only basis of the Index fund well at least in general since not all exchanges have index fund as their basis and seriously, in cryptomarket we tend to look more for the price of Bitcoin compare to altcoins.
There is Indexcoop.com which appears to be the biggest of them all (~200M in assets under management). They're backed by some known investment firms, but I would still recommend you to do more research as I haven't tried them myself.
Didn't hear about this one, looks like an interesting way to invest. I will also try to research more about this since I usually hear index fund in stock market, not familiar on any crypto index fund though.