Why there is horizontal lines all over my MacBook Pro screen?

Yes, I am still seeing them. :(

I'm so sorry. This likely means your screen is showing signs of failure. I hope this isn't the case! I'd get it checked out for sure and please let us know what they say.

I made a genius appointment in an official Apple support center. They told me that it might be a problem with the screen. And that I might replace the whole screen. I am now trying to reach the official support. I've already called them and explained my problem. I hope that my MB enter as an exception in that recall program that just appeared for people who have problems with the flex cable. Thanks for the help.

Macbook Pro 2016, with horizontal lines

This started while I am traveling abroad, with no Apple Store in sight.

After reading the comments, I tried the following:

With the display open at 40 degrees, I reached in and pressed firmly down onto the right hinge, then slowly opened the laptop to my preferred viewing angle. What I was trying to achieve is to "hold the ribbon cable in place" while opening.

This seemingly worked, as there are no more lines, until the next time.

Of course, I don't know how long this will work, or if it may damage other parts if used too often.

All I want is that this works until I am back home (another 10 days) and I can bug my favorite Apple Store to provide a hopefully free repair.

It's normal with an external monitor

That isolates the problem to your display or display cabling.