Black Screen after apple logo sapphire rx580 nitro+:
... snip ...
any ideas?
Solution is insanely simple:
1. In BIOS Features change from default Other OS to Windows 8/10
this step is essential: CSM is configurable only when Windows 8/10 Features is set to Windows 8/10 or Windows 8/10
WHQL
2. Now CSM option is visible and configurable. Change CSM to Disabled.
That's almost all, but wait.
You probably have meanwhile messed with Clover and your your Clover Graphic Configuration is most likely screwed up. Before going on you have to verify if your Clover Graphic section is adequate. Clear every value in Graphic Section
and leave just ig-platform-id. This value must reflect your actual hardware configuration. For my I3 6300 (HD Graphics 530) i have ig-platform-id 0x19120000. Select yours. Clear all other values. Disregard suggestions to enter "FB name" or "Video Ports" value.
Now set "Inject ATI"=TRUE and "RadeonDeint"=TRUE.
Now, that's really all but, still there's more.
Before using your RX580 you have to attain Graphic acceleration on your iGPU and then you'll have just to plug in RX580 and enjoy. To do so, temporary remove your RX580 from the rig or simply disconnect PCIe power cable from your new graphics card. Otherwise, RX580 would hijack your display too early and you wouldn't be able to solve the problem. Reconnect it after you have attained QE/CI and Metal with your iGPU only.
If you still do not have acceleration use the latest WhateverGreen.kext and Lilu kext. Also verify in Clover Acpi section you have adequate Patches (HDAS to HDEF, GFX0 to IGPU).
Never surrender. That isn't so hard.
NB: I have a slightly different Graphic card: Sapphire RX 580 Pulse (Device ID: 0x067df, Revision ID: 0x00e7, EFI Driver Version: 01:00.3180). However, this method would work for you too.