The crypto strategies that I’ve seen usually benchmark against BTCUSD.

Is using a single cryptocurrency for benchmarking a good idea though?

S&P has created a few different crypto indexes:
https://www.spglobal.com/spdji/en/index-family/digital-assets/cryptocurrency/#indices

In QuantConnect, is it possible to benchmark against indexes rather than ETFs?

Benchmarking strategies against a crypto index, rather than just BTCUSD, would be nice.