It is not the Android 5.0 L update for T-mobile LG G3. After the Update, Your handset Software version is D85110R.
The firmware update is available through OTA Update and LG Mobile Support Tool Software.
Several T-mobile LG G3 owners at XDA forum confirmed to have received the software update.
“My phone just got a system update of 261mb, and it looks like the software version updated from D85110m to D85110r”
For your reference, This update provides following features and improvements:
T-Mobile Free Inflight Texting support
Bluetooth connectivity improvements
Wi-Fi connectivity improvements
UI improvements for T-Mobile Free Inflight Texting suport
The D85110R software update patched the vulnerability for stump root app. So, If you want to keep the root access, please skip this D85110R software Update.
Wish this helps!