I could manage the "No Signal" Problem like this:
Change /System/Library/Extensions/AppleGraphicsControl.kext/Contents/PlugIns/AppleGraphicsDevicePolicy.kext/Contents/Info.plist from:
Do not use ADGPFix.app!
This solves the "No Signal" problem for MacPro 6.1 (Late 2013) smbios. Maybe it will also work for your smbios. Or look for any "Config1" in the Info.plist and change it one after the other to "none".
Very important: You'll need to repair the permissions of the changed Info.plist. It can be easily done with "#####" or similar. If I change my file, I copy it to the Desktop, do my edit, delete the source file and let "#####" or similar do it's part. Works all the time for years now.
Hope this helps.
One problem I've got is that I do not get any acceleration when playing h265 MKV UHD videos. Not with VLC nor with MPlayerX. Also not with the DivX Player, latest version. I'm really desperate. Does anyone have advice for me? Gigabyte GV-N970G1 GAMING-4GD with latest NVIDIA driver and latest CUDA version.