I'm on the same boat after the 10.14.6 update (black screen with HDMI on RX 580 Pulse), was working fine with kext patches that @foxbox suggested in 10.14.5.Ongoing problem... System "boots" properly on 10.14.? after "update" to 10.4.6 from 10.4.5 (which was working perfectly) on only one of my SSDs, but now booting from neither SSD gives a display. Sapphire Radeon RX 580 Nitro+ is now not even providing video to monitor from its Display Port to display my BIOS (F12 does nothing). But the computer is active and the HDD activity is there. I updated via Software Update. Tried clearing CMOS, same problem.
Any help here?
Will try tonight with a Display port cable to my monitor and hopefully works that way. I prefer HDMI as it passes audio to the monitor.