I have the same TV. It doesn’t specifically help you but using HDMI 2.1 sources works fine for 4K HDR 120Hz and VRR. I have too many devices (Xbox Series, PS5, AppleTV, Switch) so they are routed through a GUIDE3 switcher.

So I would think it is the DP converter or the HDMI cable not really being 2.1.

I was wondering if that also included the Arc of 285K, and it seems it does (in that it is not supported). Last non-pro Intel GPU that supported SR-IOV is Xe Graphics on 12th Gen…

source

I failed to get GVT-g running on 10th Gen, too unstable for a Windows VM for work. :(