Progress so far:
I had only been able to test the extension cable with my laptop + MiniDP-DP adapter (the adapter works good with 8KX without extension).
Using the 2m extension:
- In DSC (Native) mode: Not working
- in Upscale mode: Works as normal
I am not sure if the MiniDP-DP adapter might be the problem here, but it doesnt look good anyway. Getting an error 10936 in PiTool saying DisplayPort is not connected.
I somehow believe the cable does not support DSC mode. This cable is only confirmed to work with HP Reverb and I dont know if HP Reverb uses any DSC mode at all?
I will check tomorrow using the desktop PC with RTX2080Ti.
I will also order another 2m extension cable from Amazon that supports hbr2 and hbr3 DSC.