how can i force gsync on on an non compatible freesync monitor ?

i have tried to enable gsync by setting the metamode in the xorg.conf configuration file located under /etc/X11/xorg.conf . I coulnd get it to show up inside the nvidia-settings gui.
Here is gsync mentioned https://download.nvidia.com/XFree86/Linux-x86_64/430.40/README/configtwinview.html

monitor: LG24MP68VQ
GPU: 1050 ti
kernel:4.15.0-55-generic
distro: linux mint cinnamon

In nvidia-settings GUI’s display configuration you have to click “Advanced…”, then enable “Allow G-SYNC on monitor not validated as G-SYNC Compatible” and apply.

To make it more permanent I use this in my Xorg configuration (needs to be changed depending on output name):

Option         "metamodes" "DP-2: nvidia-auto-select +0+0 {AllowGSYNCCompatible=On}"

nvidia-settings should include it in the config file it can generate.

Is this configuration file valid?

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "LG Electronics LG IPS FULLHD"
    HorizSync       30.0 - 85.0
    VertRefresh     40.0 - 75.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTX 1050 Ti"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "nvidiaXineramaInfoOrder" "DFP-1"
    Option         "metamodes" "HDMI-0: nvidia-auto-select +0+0 {AllowGSYNCCompatible=On}"
    Option         "SLI" "Off"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

I saved it under /etc/X11/xorg.conf

nvidia-settings shows that gsync is still disabled. Does Gsync work over HDMI ?

The “metamodes” option line needs to be in the Device section.

To my knowledge G-Sync over HDMI will not work. It’s DisplayPort only.