I also have found a solution for the black screen issue, bootargument agdpmod=vit9696. See below. I don't know about after sleep, since I don't put it to sleep. I added this to the config plist.
Update: I put it into sleep and tried to wake up, this does not automatically happen. I don't need to hotplug anything, but I need to turn my monitor off and on. Not a problem, but an inconvenience I would say.
agdpmod=vit9696
- Disables board-id check, may be needed for when screen turns black after finishing booting
For those interested, attached my EFI folder which should work for 10.15.4, please check with seperate USB drive first and don't try to adjust config files with USB EFI and HDD/SSD EFI mounted
.I've learned my lesson about that.
I removed the board serial, serials, UUID, ROM (use MAC adress withou the : in between). Remember that only HDMI will work, you need to check the framebuffer patch for DP. I will try when I have time, I now do have DP adapter. I also disabled the BCRM (broadcom wifi and bluetooth kernel patches, simply enable by changing no to yes). You can disable picker by putting false behind show picker. Timeout of bootmenu picker 5s.
Good luck.