Internal video acceleration for games is supported only under macOS 10.14+.
If you are using macOS 10.14.6+, you can accelerate applications and games with the eGPU if they support GPU acceleration...
• Select the app in Finder
• Get Info
• Select Prefer External GPU
To get the maximum game acceleration, connect a game display to external graphics.
If you are connecting from a DVI (or sometimes DP) port on your GPU Card--via an adapter cable--to an HDMI port on your monitor and the display looks magenta, you can fix the issue in the monitor control panel. Go to the monitor Color Settings; select Input Color Format; change from RGB to YPbPr. That should solve the problem.
