I have a Chinese made Nikon lens to Canon FD body adapter I bought off eBay several years ago. It has worked fine with all Nikkors I've tried, except my AIs 24mm f/2.8. There's something on the back of that lens that prevents the breechlock ring from turning far enough to secure the lens. I can hold it onto the camera if I must. But this is no big loss, since my Canon 24mm is a better lens than the Nikkor anyway. Far as that goes, my Tamron 24/2.5 is a better lens than that Nikkor, which is notoriously unsharp in the corners.
I bought the adapter, figuring that one day I might have a Nikkor that I had no equivalent Canon FD or Tamron to match, but so far that day hasn't materialized. Maybe one day I'll get an AIs 180mm f/2.8 ED, where I can actually see using a Nikkor that Canon didn't make an equivalent of. Unless I find a deal on the Tamron 180/2.5, in which case . . . never mind.