Is it possible to hook up a GeForce [Maxwell or Kepler] to drive the display and a Radeon card as a compute device under Linux?
Yes, I have both NVIDIA and AMD GPUs in my computer. You can hook monitors to either or both, and you can use both for GPU compute. They each show up at a “platform” in OpenCL, and a “device” within the platform.
How did you install both the AMD and the NVIDIA drivers side by side succesfully under Linux?
Sorry, this is under Windows. I don’t know how to do it under Linux. I assume it is possible though. OpenCL should use the Installable Client Driver (ICD) and each would show up as a platform.