Issue with Setting NVIDIA GPU as Primary Renderer

[DAigory]

I am experiencing issues with setting the NVIDIA GPU as the primary renderer on my Optimus laptops and would greatly appreciate your assistance. I have tested this on four different laptops:

Laptop with i9 CPU and 3080 GPU

Laptop with 7700HQ CPU and 1050ti GPU

Laptop with AMD Ryzen CPU and 3070ti GPU

Laptop with 7700HQ CPU and 1060 GPU

Configurations Tested
Kernels: 6.12.x, 6.8.x, 5.15.x, 5.10.x, 5.8.x (including LTS and non-LTS versions)

NVIDIA Drivers: DKMS and non-DKMS versions 470.74, 560.35.03, 565.57.01

Settings and Attempts
I tried all possible combinations of module parameters with and without nvidia_drm.fbdev=1 and nvidia-drm.modeset=1 in modprobe and/or kernel options with systemd.

Results
Before loading SDDM or Plasma in terminal:

cat /sys/class/graphics/fb0/name
Depending on the laptop, it returns i915drmfb or amd, indicating framebuffer rendering is not on NVIDIA GPU.

sudo dmesg | grep -i drm | grep primary
Result:
fbcom: i915drmfb (fb0) is primary device (expection nvidia)

Attempts to Load KDE
X11 Configuration:

plaintext
Section "OutputClass"
Identifier "intel"
MatchDriver "i915"
Driver "modesetting"
EndSection
This configuration loads with i915.

this way:
Section "OutputClass"
Identifier "nvidia"
Driver "nvidia"
EndSection
This results in a black screen or hang

Wayland loaded system: settings -> about section shows Mesa Intel HD 630 or another integrated GPU depending on the laptop.

Attempts to Disable iGPU
I tried blacklisting the integrated GPU, but this leads to either falling back to software rendering, freezing, or a black screen on all four laptops.
I no have idea what tried else...and what i'm doing wrong or what else to try. Spend 3 days
Using downgrade package or aur 470 nvidia drivers to switch between.

My goal is not use Igpu but nvidia while renderframebuffer,kde etc