T-Mobile started seeding their first software update for LG V40 which brings camera improvements and software bug fixes. The software version on the new update bumps to V40511c which carries almost 298MB in size, and it depends on the version you are running officially on your T-Mobile LG V40. There is no confirmation whether the update carries new security patch or not. and well, this ROM is still based on Android Oreo, not Android 9.0 Pie.
As per the T-Mobile, the update is currently rolling via OTA (Over The Air) and will soon hit your T-Mobile LG V40 device running stock ROM without root. With this software update, there are no major changes except the bug fixes.
This update is an incremental update for T-Mobile LG V40. So we recommend updating your device safe with the latest security patch which has patched a whole host of vulnerabilities in Android.