Mac Pro (2019) and AMD 5700 XT

I have a Mac Pro (2019) with the the AMD Radeon Pro 580X Module.

I replaced the 580X with a RX 5700 XT (utilizing the Belkin AUX Power Cabel Kit). Running in MacOS 10.15.2 there are no problems.

When I boot the mac, the Apple Logo no longer appears. Which results in the issue of when trying to install Windows 10 via bootcamp. Neither the Display Port or HDMI will show the "Startup Manager" window on the 5700 XT. If I reinstall the 580X module, it operates as expected.

I installed windows 10 (via bootcamp) with the 580X module installed. I installed the bootcamp drivers without issue.

But when I placed the 580X module with the 5700 XT (following the "Using AMD Graphics cars with Microsoft on Mac Pro Guide 'https://support.apple.com/en-us/HT210560') the same issue occurs. I can't see the 'Startup Manager', I can hear (via display port) on the  monitor the Windows bootup (if I tell MacOS to boot into Windows). I can't get any display to show.

The issue is still present even when switching the 5700 xt and 580x module between port 1 and 3.

The question is. How do I see the 'Startup Manager' with a AMD Radon 5700 XT installed on a Mac Pro (2019) with the 580X Module Removed?