HiveMindTry "-gl" in launch options
care to explain how -gl works mate?
https://support.steampowered.com/kb_article.php?ref=1216-JMTZ-0860
-gl use the OpenGL engine GoldSource Only
And afaik, client has no control to enable d3d -> OpenGL translation.
BRZ, could you use an application like GPUZ to monitor for gpu activity while it's in the background?
That way you'll know for certain which GPU is being used.