Just yesterday, the Marshmallow update for the T-Mobile LG G4 had appeared on LG Bridge, allowing users to go ahead and flash Marshmallow on over to their LG G4 relatively easily. However, for those that did not want to deal with flashing the software onto their smartphone, the OTA appears to be rolling out imminently. As T-Mobile has posted the Support Page for the update on their website. Additionally, a few users are reporting that they have received the OTA already. Making it a pretty big deal for LG G4 users on T-Mobile.
The update that T-Mobile and LG are rolling out will bring you to Android 6.0 Marshmallow along with the January security patch. Unfortunately it looks like the February patch isn't in this update, yet. So while you're mostly up to date, you're still behind a bit, with the Nexus line being on Android 6.0.1 and the February patch. T-Mobile states that the OTA actually began on February 4th, so LG G4 users should see the notification for the update pretty soon. The update is fairly large, so you'll want to be sure that you are on WiFi before attempting to update your LG G4 to the latest version of Android.
Marshmallow brings all sorts of new features to your LG G4. Perhaps the biggest feature is Google Now on Tap. Allowing you to get information form Google Now on any page. For instance, if you are on an article on Android Headlines, Google Now on Tap would bring up information about various companies mentioned in the article. Including the likes of Sprint, Google, HTC, Motorola, Samsung and many others. Additionally you can take a screenshot through Now on Tap as well, and immediately share it without leaving that page or app. Other features include Doze, which will drastically improve standby battery on the LG G4, as well as some under-the-hood improvements all around. There's no official changelog available from T-Mobile or LG just yet, the build for this update - in case you were wondering - is H81120i. If you are on build H81110h, H81110n or H81110d, you will be prompted for the update soon. If you're on another version, it might be a bit longer for your update to appear.