Guys, same here, I tried everything you suggested no luck.
I'm injecting via DSDT, all clean, normal HD4600 from latest i7 processor id:
"AAPL,ig-platform-id", Buffer() { 0x03, 0x00, 0x22, 0x0D } (it's the only id that actually works fantastic)
Framebuffer is Native Azul, QE/CI all good, TODO fantastic ! Just one thing.. 10 sec of FUZZY analog signal before login screen ?? Connected to HDMI !
Anyone has a solution to get rid of this annoying 10 sec ...