Didn't work for my RX580, Sierra 10.12.6, SMBios MacPro6,1. Login screen fails to load.
Having said that, I edited the relevant AMD kexts. With the default pair that Sierra chooses (AMD9510 & AMD4100), my RX580 only reaches 3000 points on Luxmark.
I removed the 0x67DF1002 IDs in these both...