Has anyone out there been able to get Thunderbolt 3 to work on an X570?

There is an issue with PCIe bus number allocation on this chipset and motherboard, described here. The recommendation (adding pci=realloc,assign-busses,hpbussize=0x33 to the kernel command line) has worked for me and I was able to connect a Lenovo Thunderbolt 3 dock. However, certain other Thunderbolt devices (e.g. an eGPU) don't work for me on the system, which suggests that something else needs fixing.

EDIT: My current PCIe-related command line is: pcie_ports=native pci=assign-busses,hpbussize=0x33,realloc,hpmmiosize=256M,hpmmioprefsize=16G

This makes it possible to connect an NVidia Quadro P5000 inside a Razer Core X Chroma as an eGPU. My forum posts with details and context can be found on egpu.io, on ArchLinux forums, on NVidia forums and on Razer forums.

Thunderbolt docks still work and so do Thunderbolt 5k monitors (e.g. LG 27MD5KL, including the built-in USB-C hub, camera and audio device). (One just needs to plug the GPU's DisplayPort outputs into the motherboard's DisplayPort inputs meant for Thunderbolt.)