Green and white lines on screen of a macbook pro

my Macbook pro 13inch, Early 2015 has the problem you can see in the picture I take that to the support, they told me the screen was broken, so they replaced it, but the problem is still there. Now the weird side of the story, that issue is there just after the login screen. If I connect the macbook to an external display, both the internal and exernal starts to be well visible again! Another strange thing is that I tried to wipe everything, formatting the entire disk and installing a brand new Catalina os (I had Sierra before). All the installation went smootly in the recovery suite (without the external display connected), and the initialization of the os as well. But, after the desktop appeared, the problem was back there. When the hdmi cable is connected, the screen works perfectly fine, as you can see here I tried to reset NVRAM with the P R option cmd combination I tried also to reset the SMC with shift ctrl option combination Nothing seems to have any effect. Any idea? Thank you