could be a main board video processor issue (less likely ) as well as a bad backlight array issue (more likely). you would have to take it apart and check the video board first. Make sure that the components etc. still look okay and nothing the is obviously damaged. A bad backlight array would also explain the “screen will flicker on and off” Once you have the back removed, let us know what exact model panel is in this monitor.
To open the panel, remove the Philips screws for the frame. Start with the ones by the driver PCB. You should then get to disassemble the panel. Careful! There should be a few sheets of white “plastic” Those are diffuser sheets and need to be reassembled in the same order and the same directions. I mark mine with small stickers so I do not mess them up when I reassemble. Let me know if that makes sense"