Rootinf for LG G3

Version of Android and date of the kernel, please? Those will determine what's best. (You root Linux, not the hardware, so we have to know what your phone is running.)
 
If stump root works for the AT&T version, then that's a really easy option. T-mobile blocked that with an update so I had to use purple Drake, which was also easy but it required plugging into a computer. To get around the bootloader you have to use something called bump. All of this can be found by googling LG G3 xda