Originally Posted by smohanv
Should the script line sys.display-size=3840x2160 be found in build.prop after flashing and restarting the device right?
I don't see this script line in build.prop hence manually added.
Still could not see higher resolution than 1440. May be LG G5 doesn't support 4k videos.
Magisk (resetprop) doesn't add, remove or change anything in build.prop, it merely loads whatever value from the resetprop command to system.
Use getprop in a terminal emulator to see if the proper value is loaded.