LG V20 bootloader unlock available for unlocked U.S. devices
Unfortunately, your device's warranty will be voided, and there's no way to undo the process. But if you crave the freedom of rooting your smartphone, cleaning up apps you will never use, and tinkering with modifications, that's the necessarry price to pay for enjoying Android's open nature.
In case you want to proceed with rooting straight after unlocking the bootloader, you may use the method of flashing a custom TWRP recovery, followed by flashing the latest SuperSU .zip file. The process is easy and relatively fool-proof. Instructions are available here.
The LG V20 boasts a massive 5.7-inch 2K display, dual 16MP and 8MP rear-facing cameras, 4GB of RAM, Snapdragon 820 processor, 3200 mAh battery, high-quality DAC, and runs Android 7.0 Nougat. It's a high-end smartphone worthy of consideration, especially with the current Black Friday savings offered by LG.
source: LG Developer via Android Police