Hello guys! I was also one of the guys who was stuck on the G3 with Lollipop 5.0. Seeing the LG G4 with the great new LG Optimus UX 4.0 made me burn. So I looked up XDA to get the UX 4.0 before it was officially out for the G3s. And tadaa! I succeeded!
You need a rooted phone to get started with this.
Follow this XDA link to get started!