Also, to break unknown/unseen PRNG, model a few popular classes of PRNG, a few common reductions (so for cards the naive val%52 and better rejection sampling), then solve across the states till you get one. Then watch a few more outputs, check that you guessed the source and reduction, and now you've cracked that too.

I doubt any poker site uses anything other than a crypto rand for deals because the technique I just explained would eat them alive. They can use fast and insecure PRNG for doing Monte Carlo hand evaluation, though, since that doesn't give you any advantage.