That's interesting. I've read something different... that the "N" stands for "nominee". Per IRS "instructions for Form 8949", you should enter "N" if you ... "you received a Form 1099-B or 1099-S (or substitute statement) as a nominee for the actual owner of the property". I don't really know what that means. I thought perhaps in my case, it was because the assets were actually owned by a trust, of which I'm the trustee. But I'm not really sure.
https://www.irs.gov/instructions/i8949#en_US_2022_publink1000286502
