The update is not being sent out OTA, and requires the use of LG Bridge. That means that the phone needs to sync with a PC in order to receive the hefty file, which weighs in at 1.55GB. According to a Reddit poster, the update is available in Portugal, Poland, Romania, Germany, Turkey, U.K., Croatia, Hungary and Switzerland.
LG's own website includes a laundry list of changes that are coming to the LG G4 with the Android 6.0 update. For example, Doze will put your phone into a deep sleep, shutting down apps running in the background, notifications and alarms, when the phone is inactive for a period of time. This extends the battery life of the handset. Knock Code will now have to be comprised of 6 taps using at least three of the quarters. App permissions can be allowed or denied on a feature-by-feature basis, and Silent Mode can be enabled from the notifications panel.
One change to the UX includes the addition of the Allow Peeking feature. This allows you to read notifications on the top of the screen without the display getting covered up. You can check out all of the new features by clicking on the sourcelink.
source: LG via AndroidAuthority