It depends on whether or not your spouse’s plan offers coverage to spouses and dependents. In most cases group plans do offer coverage options for the employee, their spouse, and any dependents. In this case you as the self-employed individual would no longer qualify for any premium tax credits or discounts.
If your spouse’s plan does NOT offer coverage for anyone beyond the employee, then you can get a Marketplace plan. And depending on your income, qualify for tax credits and discounts. Keep in mind, most of the time, in order to qualify for premium tax credits and other discounts on Marketplace plans, a married couple must file a joint federal tax return.