Force Photoshop NOT to use egpu for graphics acceleration

I have an egpu connected to my mac. This egpu is only for video rendering. Photohop tells me in preferences on performance that PS will use graphic cards acceleration and uses automatically the external egpu. I want photoshop not to use the egpu but the internal graphics card which is also a good one. 

But this is not possible. 😞 Again photoshop as a pro program drives me mad. Support telling me it is not possible to force PS not to use the external one. ??? We need an update so we can change the graphics card in preference. Does onyone had an idea how I can tell PS not to use the external egpu? I am on Mac OSX Mojave.

thanks