We have seen screenshots of an Android 5.0 Lollipop update running on the LG G3 before. Now, an xda user has uploaded a working ROM that you can install on your phone and try it out for yourself. The user notes that the ROM is an early build and not very stable. Also, it is only intended for the F400S variant of the G3. If you have a F400S G3, one that you don't mind bricking or potentially making it unusable, then you can try installing the update from the source link below. If you don't want to do that, you can just watch the video below. Source ...
Source: http://www.gsmarena.com/lg_g3_android_50_lollipop_rom_gets_leaked-news-10166.php