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.
Connect one 4k monitor to the DP port.
Connect one 4k monitor to HDMI port.
Connect two 4k monitors a Sonnet Thunderbolt 3 to Dual DP or Dual HDMI adapter connected to the Thunderbolt 3 port.
macOS 14 (Sonoma) and macOS 15 (Sequoia) will crash when an eGPU is hot disconnected. It will work fine if you connect or disconnect when the computer is shut down. Sonnet has filed a bug report with Apple.