AT&T LG K40 LMX420AS Specs
Carrier: AT&T
Model: LMX420AS / X420AS
OS: Android 9.0 Pie
CPU:MediaTek Octa-core (Up to 4 x 2.0 GHz + 4 x 1.5 GHz)
Display: 5.7″ HD+ FullVision™ 1440 x 720 pixels
RAM: 2 GB
Internal Memory:32 GB
4G LTE Bands: LTE Bands 2/4/5/12/14/29/30/66
Battery: 3,000 mAh Non-Removable
The LG K40 is now available at AT&T. It comes with Android 9.0 Pie OS out of the box.
AT&T LG K40 LMX420AS User manual
Visit LG official Support for AT&T LG K40, to download ATT LG K40 owners manual
AT&T LG K40 LMX420AS USB Drivers
The latest LG USB Drivers Ver 4.4.2 can be download via this link.
AT&T LG K40 LMX420AS Stock firmware
There is no way to download the stock kdz firmware for AT&T LG K40 Smartphone.
Maybe you can use LGUP 1.16 to dump the firmware of ATT LG K40.