As I understand it, online poker is only legal in six states: West Virginia, Delaware, New Jersey, Michigan, Nevada, and Pennsylvania.
But you can still play on other websites that aren't regulated, like ACR, Coinpoker, GlobalPoker, BetOnline, Ignition, and some apps like Pokerbros.
Most of these sites use cryptocurrency for putting in money and taking it out.
From my own experience, I'd suggest Coinpoker, Ignition, or BetOnline because they're easier to win on, and they're good at keeping your money safe.