Neither Steem nor Nano seem to be a supercomputer with arbitrary computation.

I'm not very familiar with either of them, but Steem seems to be a non-centralized database of reddit-like posts. This doesn't seem to be offloading arbitrary computations to others like OP wants to do.

Nano also doesn't seem to be offloading arbitrary computations to others.

Ethereum does allow arbitrary computations, but it is not offloading, it is requiring every node to rerun every computation, which is obviously much less efficient than a single centralized computer doing the computation.