In order to have a machine that can “pick” any possible shuffle by index (that’s all a seed really is, a partial index into the space of random numbers), you’d need a seed 223 bits long.
But you wouldn’t want perfect mechanical shuffles though because 8 perfect riffles will loop the deck back to it’s original order! The minor inaccuracies are what makes actual shuffling work.
I’d probably have the machine do it all electronically and then sort the physical deck to match, not sure you could control the entropy in a reliable way with actual paper cards otherwise.