There is nothing to do; you don't qualify for the Premium Tax Credit (but see my bottom paragraph about Medicaid).
Just to clarify ... you don't need income to get Marketplace insurance. You just need it to get the Advance Premium Tax Credit.
And yes, not only do you not qualify for the credit if you intentionally disregard the rules and lie about your income, the penalty can be $100,000 for intentionally putting false information on your Marketplace application.
Have you checked if you qualify for your State's Medicaid program? If you live in a State that has fully 'expanded' Medicaid, you would qualify for free Medicaid insurance.
https://www.kff.org/medicaid/issue-brief/status-of-state-medicaid-expansion-decisions-interactive-ma...
