As per the FAA this is a privately owned public use airport, I do not observe any sign of PPR. https://www.gcr1.com/5010ReportRouter/21N.pdf Should the airport administration offer comment?

Mattituck Airport (FAA LID: 21N) is a public use airport situated one nautical mile (2 km) southeast of the central business district of Mattituck, a hamlet in the Town of Southold, Suffolk County, New York, United States. Per the FAA WEBSITE... it is classified as a public use airport. Like it or not! A precautionary landing for WX concerns ought not to have been met with hostility. Unacceptable.

Even though it is not charted, and is not noted in the AFD, PRIOR PERMISSION REQUIRED BEFORE LANDING. I diverted here due to weather and was chastised. For all practical purposes this airport is only for the use of those hangared there and a visiting helicopter. Short runway with a fine approach over the bay.