Kind of hard to say yet since I've only had it a couple weeks (and I think it's only been out for a week or so longer than that), but I did get the update to fix the BlueBorne vulnerability. Still waiting on that update for my S8+ (also unlocked). We'll know more over the next few months. Currently Android 7.1.1 with August security update (but again, with the BlueBorne fix as well).
Got my phone Sept.15 and still on August security update. The one thing I would really like to see Samsung do better on is monthly security updates. Usually a few months behind
Thanks guys for your feedback so far. I've always wanted to go unlocked but heard the update situation was bad. Hopefully more unlocked users can chime in as time goes on.
There was the one update out of the box but nothing since. To be fair to Samsung they're still pushing updates out to my unlocked Note 4.
The EE carrier version of the Note 8 (here in the UK) security update is dated September 1st I believe, if that's anything to go off.