I have pasted my system info from macOS. In my experience 18.5.2v4 is the most recent version that works without problem. Every release after that has had some or other issue sadly.
Hope this helps & thanks!!
Radeon Pro 580:
Chipset Model: Radeon Pro 580
Type: GPU
Bus: PCIe
PCIe Lane Width: x16
VRAM (Total): 8 GB
Vendor: AMD (0x1002)
Device ID: 0x67df
Revision ID: 0x00c0
ROM Revision: 113-D000AA-931
VBIOS Version: 113-D0001A1X-025
EFI Driver Version: 01.00.931
Metal: Supported, feature set macOS GPUFamily2 v1
Displays:
iMac:
Display Type: Built-In Retina LCD
Resolution: 5120x2880 Retina
Framebuffer Depth: 30-Bit Colour (ARGB2101010)
Main Display: Yes
Mirror: Off
Online: Yes
Rotation: Supported
Automatically Adjust Brightness: No