My iPhone 8 Plus screen went black/iPad mini 4 antena cable broken

Hi WM. This should really be two separate questions. That makes it easier for others to search against and it will keep the answers and comments more aligned.

For the iPad, the antennas can be repaired/re-soldered depending on the damage level. Post a picture and I’ll be in a better position to comment.

As for the iPhone, black screens can be caused by a lot of different things. It could be a dead battery, a damaged/defective screen, a logic board issue etc.

The more background details you provide (drops, repairs, water etc.) the better the diagnosis. It’s like going to the doctor and saying you have abdominal pain…the doc is going to need more info than that to give you a proper diagnosis :>).