egpu no external monitor picture

Hello, dmirkd1984.

Thank you for using Apple Support Communities.

I understand you're unable to get your Sapphire RX 58 GPU to work with an external display. I'd like to help. If you're using an eGPU, make sure to set it as a primary display as shown in this article: Use an external graphics processor with your Mac

"Set an external eGPU-connected display as the primary display

If you have an external display connected to your eGPU, you can choose it as the primary display for all apps. Since apps default to the GPU associated with the primary display, this option works with a variety of apps:

1. Quit any open apps that you want the eGPU to accelerate on the primary display.
2. Choose Apple menu  > System Preferences. Select Displays, then select the Arrangement tab.
3. Drag the white menu bar to the box that represents the display that's attached to the eGPU. 
4. Open the apps that you want to use with the eGPU.

If you disconnect the eGPU, your Mac defaults back to the internal graphics processors that drives the built-in display. When the eGPU is re-attached, it automatically sets the external display as the primary display".

Cheers!