Recently I discovered this chess variation, that is just chess but beginning after the third move. The first moves are chosen probabilistically from a random distribution of the masters games. In this way, opening theory, ie. memorization, loses importance in favor of pure chess ability.
In would be interesting to have this modality available as a new variation in lichess. I think that there is no chess portal implementing this variation.
Web describing the details:
Paper with technical details:
Nigel Short on Neoclassical Chess: