Having the same exact issue as described in this support thread, but on another model, the Q80T 49".
In the case in the link, the problem was solved by changing the refresh rate, but I have the 49" version with no 120hz option.
My graphics card is an RTX 2060 on a 49inch Samsung Q80T 4K TV with maximum refresh rate of 60hz. Have tried different resolutions.
The line at the bottom of the screen is continually delayed from the rest of the screen whenever my PC is using the TV as display with Game Mode on. It’s not random flickering like "normal" screen-tearing. The problem can be seen on the link below.
Hope someone can help