Dual nvidia, triple monitor xorg configuration

Hi, I’ve tried and googled a lot, but I know when I’m beat.
So I have a laptop, I could plugin a razer core in and configure more or less to have everything working, the problem is that not everything works at the same time.
Precisely, I don’t manage to make both my gpus work at the same time. Which means either I have my built-in monitor working, either I have my 2 external monitors working, but I can’t find a way to make all 3 working at the same time. And I’m out of ideas.

This is my working eGPU version xorg :

Section "ServerLayout"
    Identifier     "Layout0"
    Screen         "Screen0" 0 0
EndSection

Section "Module"
    Load           "modesetting"
    Load           "extmod"
    Load           "dbe"
    Load           "type1"
    Load           "freetype"
    Load           "glx"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce RTX 2080 SUPER"
    BusID          "PCI:61:0:0"
    Option         "AllowEmptyInitialConfiguration"
    Option         "AllowExternalGpus" "True"
EndSection

Section "Device"
    Identifier     "Device1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "Quadro M620"
    BusID          "PCI:1:0:0"
    Option         "AllowEmptyInitialConfiguration"
    Option         "AllowExternalGpus" "True"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Samsung LC27RG50"
    HorizSync       255.0 - 255.0
    VertRefresh     48.0 - 240.0
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "Samsung C24F390"
    HorizSync       0.0 - 0.0
    VertRefresh     0.0
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor2"
    VendorName     "Unknown"
    ModelName      "LGD"
    HorizSync       0.0 - 0.0
    VertRefresh     0.0
    Option         "DPMS"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "nvidiaXineramaInfoOrder" "DFP-6"
    Option         "metamodes" "DP-2: 1920x1080_240 +1980+0, DP-5: nvidia-auto-select +0+0, DFP-3"
    Option         "SLI" "Off"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "Device1"
    Monitor        "Monitor2"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "metamodes" "nvidia-auto-select +0+0 {AllowGSYNC=Off}"
    Option         "SLI" "Off"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

If I replace the second line of the serverlayout :

Section "ServerLayout"
    Identifier     "Layout0"
    Screen         "Screen1"
EndSection

Then it uses the built-in monitor

If I dare putting both in like this :

Section "ServerLayout"
    Identifier     "Layout0"
    Screen         "Screen0" 0 0
    Screen         "Screen1" RightOf "Screen0"
EndSection

Section "ServerFlags"
    Option         "Xinerama" "ON"
EndSection

Then it tells me that Xinerama on with Composite extension enabled is not supported and in fact > nothing works, I get black screen on built-in, nothing on the others, but I can move my mouse around on the built-in.

if I disable Composite :

Section "ServerLayout"
    Identifier     "Layout0"
    Screen         "Screen0" 0 0
    Screen         "Screen1" RightOf "Screen0"
EndSection

Section "Extensions"
    Option         "Composite" "Disable"
EndSection

Section "ServerFlags"
    Option         "Xinerama" "ON"
EndSection

Then the login doesn’t work, crashes and tells me to log out and retry (so rude).

So I’m at this point, I really don’t know X server nor NVidia, so I’m out of ideas, please help me.

For info I have :

  • Ubuntu 20.04
  • lightdm as display manager (but it’s the same results with gdm3)
  • Quadro M620 for internal GPU
  • GeForce RTX 2080 Super in the Razer Core (eGPU)

Thanks for any suggestions, if you need logs tell me of which tentative, I’m saving them all :D

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