I have a q90t and a rtx 3080. I can get 4k/120hz/Vrr with HDMI 4. The problem is programs like kodi can't adjust the refresh rate without a black screen. For example In Nvidia control panel if i go from 3840x2160 120/60hz to 3840x2160 23/24hz Tv loses signal. But if i go from 4096x2160 120/60hz to 3840x2160 23/24hz it works just fine.So if i change the resolution and refresh rate it works, but if i try to just change refresh rate i get black screen. Also ocasionaly If i have HDR on in windows and turn it off it will cause distorted image signal going to HDMI 4 which means i have to switch resolution and frequency to fix it. NONE of these issues are on HDMI 1-3. Current firmware 1460.9. Model # QN65Q90TAFXZA Latest Nvidia 461.09 Driver 10 Pro Build 19042.685. If i can't get this fixed soon ill be returning my set since this is a major issue for me.
The HDMI 2.1 support is a joke right now on this TV. I'm having all kinds of problems at 4K 120hz with VRR on a 3080.
I wish I could return it and go with the LG, but that ship has sailed for me.
Instead, I have to turn off input signal plus and hope Samsung will deliver a firmware update that fixes VRR and 120hz.
I by chance tried port 3 and for some unknown reason i can get 4k 120hz vrr . Don't ask me why the hdmi 2.0 port does everything the hdmi port 2.1 is supposed to but it does. Just try various cables and dont forget to turn on game mode for the vrr. The hdmi 2.1 port still has major issues though which is kinda ironic.