External GPU Thunderbolt docks are *so* 2016. These PCIe x16 adapters will accommodate an MXM 3.x Type-A or Type-B GPU from either Nvidia or AMD for connecting straight onto a standard PC motherboard.
https://www.notebookcheck.net/Eurocom-MXM3-Riser-Cards-will-power-your-desktop-with-a-laptop-GPU.241042.0.html