I was able to do it, and I'm not rooted.
You'll want to follow the directions laid out, making sure you do the "Normal Flash", not the "CSE Flash".
The only sticking point for me was that I didn't put my phone in "Download Mode" (I didn't see that part of the instructions!), but it worked anyways... I think it just made it take a bit longer, but I'm not sure. Here are the rather long instructions for putting the phone into Download Mode:
LG G4: How to Boot into Download Mode As I said, I didn't do that step and still succeeded.
Note that it does take quite a while for the full process, including a rather lengthy "optimizing apps" (optimizing 1 out of 81... optimizing 2 out of 81... etc.) part.
You won't lose any of your data, and it doesn't install any Telus bloatware onto your phone.