Hardware: Dell XPS 15, Win10, internal GPU GTX1050, external GPU GTX1080Ti (in Akitio Node via Thunderbolt 3)
Blender: 2.78c (also 2.80)
Latest versions of Thunderbolt drivers, akitio firmware, nvidia drivers
Just using the notebook without the external GPU: everything works fine.
Also the eGPU works correctly (nvidia control panel shows both GPUs, monitor on eGPU works, games and benchmarks work, ...)
But when the eGPU is connected to the PC, there are no more GPU options in the user preferecens "cycles compute device" (it only shows "None" ... not even the internal GTX1050 that always works when no 2nd GPU is connected)
I just bought the Akitio Node + GTX 1080 Ti in hopes to speed up rendering times and the setup works as one can only dream of EXCEPT for what I actually wanted to use it for: blender cycles :(