T-Mobile has put out security updates for the Samsung Galaxy S8 and Galaxy S9 families, as well as the Galaxy Note 8. The productivity-focused phablet is getting bumped up to the August security bulletin along with its newer Galaxy S9 siblings, while the year-old Galaxy S8 flagship family is getting the July security bulletin. As a bonus, the Galaxy Note 8 is getting what's called a "Samsung VOC fix", though it's a bit of a mystery as to what that may be. It isn't found on any other phones' update pages for this round of patches.
The August security bulletin that's hitting the Galaxy Note 8 and Galaxy S9 range contains, along with Google's fixes, eleven security patches from Samsung. It's worth noting that Samsung actually released two different August security updates for the Galaxy Note 8, with the second dropping on the same day as T-Mobile's update. This likely means that the update for the Galaxy Note 8 is based on Samsung's first issue, and the second one will come in the near future, or be supplanted by the September update in due time. As for the July security update that Galaxy S8 and Galaxy S8 Plus owners should be expecting, it has a grand total of four security fixes that are device-specific and were put in place by Samsung rather than Google.
Samsung's newest devices are obviously in line for the newest updates, but the company is not neglecting buyers of last year's flagships, either. Whichever device you happen to own, the procedure for updates is the same; make sure your battery is at least 50% charged before taking an update, though having your device plugged in is safer, and preferably do it on Wi-Fi. The update should be coming automatically in the next few days, but if it doesn't pop up soon enough for you, you can always head to your device settings, then the "About phone" area to check for updates manually. If that doesn't net you the updates you seek, try rebooting your device. If all of that doesn't work, you'll simply have to wait. T-Mobile has implemented daily limits for some of these updates, and once those are exceeded, no more users can pull the updates until the next day.