Hi @fitz50 ,
Can you still take pictures OK and see them when they are downloaded to a computer? I realize that you cannot see what you’re taking in the camera’s LCD screen but maybe this will tell you if it is a screen problem or more of a motherboard problem.
The metal contacts on the SD card may have shorted out some components on the motherboard and caused some electrical damage. If the battery was still in, there is always power on the motherboard even when the camera is off as the power switch is not a power isolating switch. Think of the camera as being in an extremely low power state when off and not totally disconnected from the battery power supply.
Alternatively the card may have physically damaged some components.
Hopefully it may be simple like the LCD screen flex cable may have become disconnected from the motherboard.
The only way to know is to open the camera and check.
Here’s the Ifixit GoPro Hero5 Blackのマザーボードの交換 guide, that may help you to find out.