Dimensions wont start on Macmini with eGPU?

[sönked74773613]

Hello, i have a macmini 2018 with an external GPU and Mojave 10.14.6.
The e GPU is a Radeon RX Vega 56 8 GB.
Is there a possible workaround to start Dimensions on my hardware?
The open GL version seems to be too old.
But how to update open GL?
When try to start dimensions following error occurs:

[Ussnorway]

correct a eGpu does not meet the min requirements

[sönked74773613]

Thank you.
It is sad that I can no longer use the program on my computer…

[sönked74773613]

I can start Dimensions when unconnect the eGPU but my Eizo maindisplay does not run then.
Whenn i connect the eGPU Dimension quits again.
Is it possible to define the GPU which Dimensions has to use? The internal is weak but seems to be used by Dimensions.
Why does Dimension not use external GPUs? 
My Radeon RX Vega 56 8 GB is quiete powerful…