This, from Turbo Tax help:
If you know you have a marketplace plan but aren't sure which type you have, you can contact the marketplace who provides your coverage.I f you enrolled in a plan directly through a health insurance provider (Blue Cross Blue Shield, Kaiser, etc.) you do not have a marketplace plan. You can answer no to the marketplace question. If you're covered through your job or have health insurance through the VA or Tricare, your plan isn't a marketplace plan, but it still counts as health care coverage. Go back and select no when we ask if you were enrolled in a marketplace plan.