You have to ask Healthcare.gov when they consider the tax return to have been filed. If they say that mailing it today is not good enough, but they will be satisfied if you e-file it today, a local tax professional should be able to e-file a 2023 tax return for you today. But you only have a few hours left. If you do mail it, take it to the post office and get a receipt to prove that it was mailed.
