The Seaplane Pilot Association
https://www.seaplanepilotsassociation.org or AOPA would be the people to call. Here is a good start:
https://www.seaplanepilotsassociatio...landing-areas/
The FAA doesn't care what happen on the water - that is a local determination whether a floatplane can land on the water or not.
But generally, a private lake can set it's own rules as far as I know. But an HOA bylaw might not have much enforcement ability against a non-owner. I believe that would require a actual law of some sort. But you're getting into what your state considers law, whether the HOA bylaws are laws, and it gets into the nitty-gritty pretty quick.