Success with LG 34WK95U-W via TB3 of GC-Titan Ridge on ASUS Prime X299 Deluxe
While connecting the LG34WK95U-W under macOS via one of the DP1.4 of my Sapphire Nitro+ Vega 64 worked basically out of box, it took me several weeks to also properly connect the display via one of the TB3 ports of the GC-Titan Ridge on my ASUS Prime X299 Deluxe.
By connecting both GC-Titan Ridge mini-DP input connectors with the two DP1.4 ports of my Sapphire Nitro+ Vega 64, macOS always implemented two LG HDR 5K (LG HDR 5K 1 and LG HDR 5K 1) monitors although just one was connected, a problem that was really annoying and that prevented a proper function of the LG34WK95U-W via TB3.
Today, after a break of several weeks, I connected by chance just one of the two GC-Titan Ridge mini-DP input connectors with one of the the two DP1.4 ports of my Sapphire Nitro+ Vega and voila... the LG34WK95U-W was suddenly properly implemented as a single monitor also via TB3 under macOS.
By this of course just one out the two TB3 ports of the GC-Titan Ridge carries the DP1.4 signal but by this the LG34WK95U-W works absolutely flawless.
At first place, I was running the monitor via TB3 under native 5120 x 2160 pix resolution, although by this the text is tiny and hardly readable.
I then switched to a HiDPi resolution of 2560 x 1080 pix
which still allows native 5K screen resolution at 2560 x 1080 pix UI resolution.
However also with this UI resolution I did not feel very comfortable.
I therefore continued trying different HiDPi resolutions, and found an UI resolution of 3360x 1417 pix and effective resolution of 6720 x 2834 pix (interpolation)
as well as an UI resolution of 3840x 1620 pix and effective resolution of 6680 x 3240 pix (interpolation)
the most convenient choices for the size of the LG34WK95U-W.
Switching between all available resolutions works flawless.
Below the active scaled resolution profile in SwitchResX.
Also display HotPlug via TB3 is fully supported, always provided a proper implementation of SSDT-X299-TB3HP.aml in the EFI-Folder.
Remaining issue with GC-Titan Ridge on ASUS Prime X299 Deluxe: Black screen on wake from sleep. One needs to unplug/replug the power cable of the LG34WK95U-W, to make it work again via TB3 after wake form sleep. It would be interesting to know if the latter is a firmware issue of the LG34WK95U-W when connected via TB3 or if the monitor such properly works with the GC-Titan Ridge on the ASUS X299 Sage (10GB). If the latter is the case, the wake from sleep issue would be very likely ASUS Prime X299 Deluxe firmware related.