root LG G3 D850 not working

[tonyvr4]

I am trying to root my LG G3 D850 so that I can install Lineage OS. But nothing seems to be working.

The phone is recognized by my Windows 7 PC.
I have adb on my computer and it recognizes the phone if I issue "adb devices"

I tried stump root and it will not install. I have allowed unknown sources.

I have also tried purple drake and it recognizes the phone, reboots it, then the script closes with no messages or indication of what happened.

I also tried "LG One Click Root" by avicohh. It reboots the phone into Firmware Update mode but it never does anything after that. I have left the process running for at least 10 minutes and it never downloads anything and the phone Firmware Update screen shows 0%

Any help is greatly appreciated
Thanks

 

[tonyvr4]

Downloaded Stump Root 1.2.0 and it displayed a message "Device is Patched. Sorry.

The phone is on Android 6.0, Build MRA58K

What is the easiest way to upgrade this to some Android Version 8 or similar ?