I need Mac Drivers for my XFX AMD Radeon RX 580 8G for my Mac Pro 2008 running Catalina

Does the card not work out of the box? There should be drivers in macOS for that model. Does the card have Apple boot ROMs? What is happening with it?

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If it works fine, then you have the driver. I searched AMD, and I did not find any drivers for macOS specific to that card. I'm reasonably certain that the current driver is built into macOS.