The LG 5K2K let you set the Thunderbolt input to use DP 1.4.
Using a MacBook Pro (also Titan Ridge), this leads to a black screen; but I've read report that DP1.4 wasn't supported on the MBP.
However, I just got a Lenovo X1 extreme, which also has a Titan Ridge chipset; with the LG 5K2K connected via TB and the LG set to use DP1.4 I do get a picture; however it is slightly distorted, and I wonder if that because the TB cable that comes with the LG isn't shielded properly.
It would be great if it did work, it would allow to connect two LG2K screen to a Titan Ridge system (when using DP 1.4)
Well I was using the LG 5K2K via TB of the GC-Titan Ridge on my X299 Deluxe with the monitor setting of DP1.4 for TB3 without major issues, although the monitor was implemented twice under macOS (persistent macOS bug I guess). With these settings, the monitor fully worked with native 5K resolution, even after removing one out of the two DP1.4 to mini-DP adapters between the GC-Titan Ridge and my Nitro+ Vega 64 (and in this case the LG 5K2K was only implemented as single monitor with 5K resolution under macOS). Thus, without any doubt one should be able to use 2x LG 5K2K at native 5K resolution via the 2x TB3 ports of the GC-Titan Ridge. However, I doubt that there is any real benefit in driving two 2x LG 5K2K displays via the two TB3 ports of a GC-Titan Ridge on a state-of-the-art Vega Hackintosh system, as even up to 3x LG 5K2K could be directly driven by the 3x DP1.4 ports of any standard Vega. In my personal opinion, the DP1.4 TB3 connection is only mandatory for connecting two different systems with the same LG 5K2K under native 5K resolution like in my case.
There are some compatibility issues between the LG 5K2K/GC-Titan Ridge/Vega 64/X299 Deluxe during system cold boot though (independent from using Windows or macOS), i.e black screen during BIOS splash screen, Clover boot manager, verbose boot message, while during a warm boot (system reboot or system reset) everything works fine once properly initialised under macOS or Windows. The system wake issue under macOS with TB devices connected to the GC-Titan Ridge on the X299 Deluxe during sleep also states for the LG 5K2K, when driving the latter via one of the two TB3 ports of the GC-Titan Ridge.
My upcoming tests with the WS Sage 10G should show if the remaining GC-Titan Ridge problems can be entirely removed by using the latter motherboard.