Macbook pro horizontal flickering lines across the screen

Connect an external display and enable mirroring. If the issue only occurs on the built-in Display, then you have a hardware issue with the laptop's built-in Display which will require getting the laptop repaired.

If the issue occurs on both displays, then it can mean you have a software issue or a Logic Board issue. It would help to know the exact model of the laptop since some models are known to be prone to GPU failures. You can get the exact model by clicking the Apple menu and selecting "About this Mac" or by entering your serial number on the following Apple page:

https://checkcoverage.apple.com/us/en/

The horizontal flickering started after the last IOS update for me. I see where a number of people have indicated that the issue started showing up in late August - which is around the same time as me. Can this issue/fix be addressed by an IOS version update?