Samsung has released its Galaxy S9 and Galaxy S9+ back in March this year, but it seems it's not serious with the Android security updates. The flagship models receive the Android security update on its release date, but surprisingly the AT&T versions of the phones lack all the updates. On the other side, the T-Mobile Galaxy S9 and Galaxy S9+ each started to receive the security patch in the middle of April, but unfortunately halted on the next day and it was never resumed since that day.
Meanwhile, the Verizon and Sprint models received a new software update (G960USQU2ARE6 for the Galaxy S9, and G965USQU2ARE6 for the Galaxy S9+) which contains the May security patch. Moreover, the Samsung official website mentions that the two new flagships are subjected to receive monthly security updates, but the carrier based models will only receive quarterly updates. According to Samsung blog post, "some carriers may only support quarterly updates for all applicable current models listed above."
So if we see the progress of the Sprint and Verizon Galaxy S9 and Galaxy S9+ both the smartphone has received the security patch back in February and after three months it received the next update. This clearly means that some US carriers are relying on a quarterly schedule to push out the security updates.
However, the AT&T models have never received any update since the launch date of the phone, and T-Mobile never completed the update which was suspended on the second day of the rollout.
If we see last years Samsung Galaxy S8 and S8+ both the smartphones are receiving monthly security updates in the US from the same carriers. Just to recall, the Galaxy S9 comes with a 5.8-inch Super AMOLED Infinity Display with an aspect ratio of 18.5:9. The bezels around the display are even narrower than last year's Galaxy S8.
Under the hood, the smartphone is powered by the in-house Exynos 9810 processor coupled with 4GB of RAM. There are two storage variants of the Galaxy S9; the basic one comes with 64GB of internal storage, whereas the higher model comes with 256GB of internal storage.
The Samsung Galaxy S9+ is fitted with a larger 6.2-inch Super AMOLED Infinity Display with 18.5.9 aspect ratio. It is driven by the Exynos 9810 processor as well, but it packs 6GB of RAM. The smartphone is available in two storage variants; 64GB and 256GB.