This project allows USB-C monitors to be connected via DisplayPort. Specifically, this was to connect a Mac External Graphics Development Kit to the USB-C only LG Ultrafine 4k, but should work with other eGPU and monitor configurations.
Various designs of this have been in use since September 2017, initially with a single Ultrafine, but now running a multi-monitor setup for times when only 12'288 horizontal pixels will do! It works with both macOS and Windows running on the same machine (under Boot Camp).