T-Mobile has started pushing the May security update out to the Samsung Galaxy S8 and Galaxy S8 Plus devices this week according to the screenshot below, which shows one T-Mobile user receiving the notification that a new update was available. As is common with software updates the changelog is listed which details the changes that a user can expect from the update once the process has been completed, and in this case the update for the T-Mobile model doesn't look like it includes anything with the software this time around that is specific to the T-Mobile network, which means the changes included will be the same as on other carrier versions of the device, save for any carrier-specific adjustments or improvements that might be added.
As mentioned above this software update includes the May security patch so both phones will be pretty up to date on the security side of things, though the June security patch will be ready any day now so the devices will still be a month behind before too long. Other changes include some improved stability to the SD card, though it doesn't mention anything specifically in terms what was not as stable with it before this update.
The last change is an update to the Bixby application and feature but there is no detail as to what has changed if anything, or if the update to the app was simply about improving performance and stability just like with the SD card function of the phone. The changelog says the update can take about ten minutes to fully complete so users will want to make sure they have the time to set aside and wait for things to finish, and the update is almost 376MB in size so it could take at least a minute or two to download before the installation process begins depending on how fast the internet connection is that the phone is connected to. As always it's a good idea to make sure that you have enough battery life on the phone before starting the update, but the phone shouldn't let you initiate things if the battery is too low in the first place. Although the screenshot below is from a T-Mobile model, users with other carrier versions should be checking to see if the update is available on their devices, and checking for an update manually can be done by going into settings, then to about phone and tapping on software update.