GameMode not working with HDMI 2.1 (RTX 3090),Samsung 2020 QLED [1402] Update !!!!!!

[RouDeR]

Background:
TV is 75 inch Q800T (EU version), but I assume this will affect all of the 2020 Samsung TVs
Software is version 1402.6 (updated Octomber 8th)
HDMI Cable 2.1 certified full 48gbps
The same HDMI cable works just fine with HDMI 2.0 GPUs like my old GTX 1080Ti (Game Mode works flawlessly there)
Current GPU:  RTX 3090 with latest Nvidia drivers

What is working as intended when using the HDMI 2.1 port and RTX 3090 as a source::
* Outside of game mode I don't have any problems, I can run at 4k@120hz RGB 10 bit or 8k@60hz 4:2:0 10 bit without any problems.

What does NOT work when using the HDMI 2.1 port and RTX 3090 as a source:
* If you turn on Game Mode, the TV picture goes BLACK and it looses signal
This happens disregarding on what resolution and refreshrate you are playing, I`ve tried the following:
- 1440p@60hz Input Signal Plus ON
- 1440p@60hz Input Signal Plus OFF
- 1440p@120hz Input Signal Plus ON
- 4k@60hz Input Signal Plus ON
- 4k@60hz Input Signal Plus OFF
- 4k@120hz Input Signal Plus ON

- 8k@60hz Input Signal Plus ON
NONE of them was able to switch to Game Mode !!!

However
If the RTX 3090 is connected to one of the HDMI 2.0 ports of the TV, Game Mode is perfectly functional, but then you are restricted to 4k60hz and 8k@30hz

SUMMARY:

Spoiler

Game Mode does not work AT ALL on the HDMI 2.1 port when HDMI 2.1 source is Attached.

[Members_I2yRBAI]

Well I struggled forever to get this to work with the same setup on q qn90b, eventually I have a method.

First keep TV mode non GAME.Then   set HDMi out on 3090 to 1080p 60Hz.

Then go into NVidia control panel and create custom resolution with 3840x2160 120Hz

. Then select the custom resolution in the list in the control panel and activate.

At this point  everything should still be ok.

Now change TV to game mode. The Image will cut out

. BUT what you will find is the TV has been deselected under the "set up multiple displays" menu in NVidia control panel.

Retick the tv in that menu and go and select your custom resolution again.

AT this point the TV will work again. Now head over to nvidia Gsync and enable settings for the TV. Walla.

This is the only way that works for me ever time i reinstall windows or something.