I successfully uprooted today. Just go to Ida developers forums search unroot LG g3 at&t and you'll find step by step list using the LG flash tool. Its pretty easy, doesn't take a ton of time. I hit some issues where you need to use a USB 2.0 and lg cable for this method so be aware of that, luckily I had both, had to try few USB ports before it worked.
Also I made a back up using the lg g3 back up in the stock ROM before this all and used that to restore my apps. Basically makes back up file on phone (about 5gb) then moved to PC. Then moved back to phone after flash and it came up when I went to restore on the phone.
Little choppy explanation but hopefully helpful some.
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