You should be able to purchase any plan on the .gov or related connector sites. The catch is you don’t get the freebies[subsidy], from what I understand you can purchase any plan as long as you can afford it.
Yes, I could in theory purchase any commercial (non-exchange) plan. But they will not allow me to purchase off the exchange, because my income is TOO LOW! So it’s Medicaid or nothing. I could exaggerate my income to get on the first year but don’t want the hassle when it catches up to me.