Sapphire Pulse RX 560 is fine also. I don't know what other specific models have been tested.
There are, or were (not sure which of them are still available new), numerous versions of the Sapphire Pulse RX-560. They fall into both categories I discussed above, so people considering them should check out which version they are getting - if it matters to them. Again, to most people it probably won't matter if it requires an aux power cable or not, whether it's a 45 watt, 60 watt, 75 watt, or 90 watt card since they are all very low for Mac video cards, and the difference is less than 15% whether it is a 16 cu or 14 cu card. There are also slightly different clock rates for different cards, but those differences are slight. But if you do care, then look carefully at the specs for the Sapphire card you are considering.
This is the only officially Apple supported RX-560 card (Apple calls it the MSI Gaming Card):
MSI RX-560 AERO ITX 4G OC 16 CU/60W/no aux power cable supports 3 displays (DP/HDMI/DVI-D)
This is apparently a new card? (I've never seen one for sale, reviewed, or discussed outside of MSI website yet):
MSI RX-560 AERO ITX 4G OCV2 16 CU/60W/no aux power cable supports 4 displays (DP/2xHDMI/DVI-D)
These are the Sapphire Card Versions:
SAPPHIRE PULSE Radeon™ RX 560 4GD5 11267-00 16 CU/90w/requires one 6-pin power cable
SAPPHIRE PULSE Radeon™ RX 560 4GD5 11267-25 16 CU/90w/requires one 6-pin power cable
SAPPHIRE PULSE Radeon™ RX 560 4GD5 11267-01 16 CU/45w/no aux power cable
SAPPHIRE PULSE Radeon™ RX 560 4GD5 11267-18 14 CU/75w/requires one 6-pin power cable
SAPPHIRE PULSE Radeon™ RX 560 4GD5 11267-20 14 CU/75w/no aux power cable
There are also 2GB Sapphire versions, but I wouldn't want one of those:
SAPPHIRE PULSE Radeon™ RX 560 2GD5 11267-13 16 CU/45w/no aux power cable
SAPPHIRE PULSE Radeon™ RX 560 2GD5 11267-22 14 CU/45w/no aux power cable