Multiple GPUs with multiple display

Hi, recently i gotten a workstation with 3 x RTX A4000, and i was trying to display 12 screens using these 3 GPUs. I am able to get 4 display running on a single GPU, but when i attached displays with more than 1 GPU, it only works for display connected to the main GPU.
I know that having PRIME DISPLAY will allow the multiple display and multiple gpu to work seamlessly. But i wasn’t able to get the PRIME DISPLAY when i plug in the second GPU display onwards; it just shows ‘Disabled’.
My system specs:
Ubuntu 18.04 LTS
3 x Nvidia RTX4000

Have you found any solution yet ?
We would like to display into 8 monitor, we are also searching a solutions.

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