If you haven’t already, check for Nouveau support. And if your card is supported, you may need a kernel parameter. I needed nouveau.config=NvClkMode=15 (but be warned some parameters like that have some risk, like possibility of overheating, and may or may not be applicable or safe for your GPU).

For me, it has worked to just set environment variable DRI_PRIME=1 to use the Nvidia GPU for that specific application. (Maybe this is what Bumblebee does; I don’t know.)

In the future, though, I recommend avoiding Nvidia hardware.