NAC and the FDA
In July of 2020, the FDA sent out warning letters to manufacturers that current rules would prohibit the labeling of NAC as a dietary supplement as it was first approved as a drug. The Council for Responsible Nutrition that is a primarily a supplement manufacturer advocacy group, responded basically saying that NAC has been marketed as a dietary supplement for decades and that this action violates FDA protocols.
I would also add that NAC has been shown to be a safe and effective supplement.
As of this writing in mid 2023, we haven't heard any more on the subject and NAC is still available from many manufacturers.
BetterGenix NAC
To brush up on your NAC knowledge, start with the following blog.