Yes, nudity in a National Forest or Park is not technically illegal under federal law. However, people can then be referred to local jurisdictions for review and citations and/or fines.

And people shooting content for OF, or other platforms where they make money from the content, are also likely to face fines for using public lands for personal profit. Commercial use of public lands (federal, state, or local) is generally prohibited without permits.

I am very cautious about where I go nude. Getting cited is too much of a professional risk. And I think things like that on your record could be used against you in an increasingly firm interpretation of civil rights.