The note 1 was NOT updated to jellybean, not OTA to the masses. That jellybean build was the buggy POS I was talking about they buried on their website , you needed a bunch of weird third party tools and a PC to install it, and when you did it basically bricked the phone. And they stuck on their website at the time saying "this is the last update for this Legacy device", so whatever was in there, was it. That build, basically didn't work without a bunch of hacks.
Well, mabey they took enough complaints to heart,and improved their update process, and your definitely right that carriers can block releases at their whim, although I don't think that was the case with the note 1 as it was the same for verizon & AT&T people.
My brother in law was on verizon with his s5. He claims it is still on the kitkat and no update has been issued, and he means automatically through his carrier. Probably you can find an update on samsung website, but...you shouldn't need to go there, or have to use third party installers and PC's to "update" your phone. That very 1990'ish!