My wife has her health insurance coverage through the Health Care Market Place which determines the amount of her subsidy according to household income.
The Market Place requires that any changes in household income must be reported.
Does anyone know if his stimulus money must be reported as an increase in income?

What a great question and the short answer is nobody know what will happen regarding those stimulus checks yet. I doubt the government knows at this point.

https://www.truthorfiction.com/is-a-1200-coronavirus-stimulus-an-advance-on-2020s-tax-credit-or-a-loan-you-have-to-pay-back-in-2021/

I did see where folks were asking if this stimulus money is going to have
to be claimed as income at tax time at the end of the year and some were
saying NO, it would be considered as non-taxable income. I don't know if
that was an official answer from the govt or just someone's personal opinion.

I have not seen a government response to your question. Hopefully one will be forthcoming.

Thanks for the replies. I guess maybe I'm asking the question too soon. You are right in that possibly even the govt. doesn't even have an answer as of yet.
I guess I like to be on top of things so we don't have any surprises.

Thanks for the replies. I guess maybe I'm asking the question too soon. You are right in that possibly even the govt. doesn't even have an answer as of yet.
I guess I like to be on top of things so we don't have any surprises.
I checked several reliable sites:

"Any money you receive will not be considered taxable as the IRS considers it a credit, or money you’ve already paid that they’re giving back to you."