I currently have a LG Stylo 5 phone and was trying to change the lock screen picture I couldn’t. I tried both methods 1. Hold down the home screen and go to lock screen settings. This then only gives me the option to use the default wallpapers that are on the phone, not my pictures. 2. Go to gallery then use picture as lock screen. I tried it and it only gives the option to set the main wallpaper.