Yes, Medicare qualifies as health insurance coverage, but it is not a marketplace plan (where one is required to enter 1095A information.)
Therefore, on the screen asking about Obamacare, etc, you would answer NO that you did not buy health insurance through the marketplace, since you had Medicare coverage and that is not a marketplace plan.
Initially,on the first health insurance screen when asked about health insurance, state that you had coverage all year. Then on the screen asking about Marketplace insurance, answer NO as noted above. Then you should be all set, as that should be all that is required for you to enter.