Broken screen, no service

So a while back i brought a broken s8 phone, since i like to do repairs. I’m not entirely sure if the insides have been tampered with although it appears so. The speaker module flex cable is broken, but that part is cheap so its no big deal. The much bigger problem is that the phone does not connect to a network when i put in a sim card and just shows a no sign where signal should be. The screen works, but only on lower lighting (turns green white if i set the brightness higher).

Following the cables, i found that the cables go under the daughter-board into the screen. My question is, is the antenna part of the screen and would replacing the screen fix this issue, or could there be another reason? Apart from the speaker module nothing else seems damaged.