I'm going to add to this because I just got my Sapphire RX580 Nitro working with macinabox and it was a PAIN! So first thing with these cards, the HDMI ports will not work in macOS, you need to use Display Port for the output. Secondly you need to dump the vrom and use that file, without it I still just had a black screen. But here is the thing... Our cards have a multi-bios feature. A physical toggle on the card. If you have NOT flashed these and the card bios is as it was from the factory, one of them is a quite setting and the other is a more aggressive overclock performance tuned. If you got the card out of your old gaming rig or a mining rig most likely that is set in performance mode. Now MACOS only likes the base bios the quite version. So power down, toggle that switch and make sure to re-dump the vrom from this setting. After adding that vrom in the setting the system booted right up (on DP :)) In theory you could then toggle the switch back but use this VROM and you can get the performance tuning in your other VMs but I haven't played with that yet!