EXTERNAL GPU NVIDIA OVER THUNDERTBOLT OVER THUNDERBOLT

Officially, Dell has no eGPU support for this model, so if you're looking for Dell support for the project,, no.

You may be able to find an eGPU that works (with an external screen, as there's no guarantee the eGPU can display on the internal one, and even if it will, you'll end up with only a fraction of the performance the GPU is capable of).

Your best bet is to search for evidence from someone who's succeeded and purchase the same GPU and eGPU box they used -- that will improve the odds that the project, which will be experimental at best, succeeds.