Screen hotplug won't work after booting headless

I have this situation that I couldn't find any solution on web after extensively searching for...

I have this PC that I use "as server" with Ubuntu-server which I then later added default GUI (GNOME Shell). It has dual video card (Onboard Intel Graphics + nVidia Geforce 1050Ti) and most of the time I need to boot it without any screen connected to it. But sometimes I need to connect a screen to have access to the GUI and it just can't happen after booting without screen. For this, as workaround, I have to reboot the computer with the screen connected and then it brings GUI successfully.

It happens on both GPU. So I have no clue on what's going on and how to work around it.

Is there any way I can set a default active GPU even without screen during boot? I can imagine this will "fake" a connected monitor on, let's say, Intel iGPU and everytime I connect a monitor on it, a GUI will be ready to be used.

Or is there any other solution for this?

For this, I don't need to use dGPU (nvidia) with monitor because I am using it to process some researches with CUDA. So I don't want to lose VRAM memory by sharing it with GUI. For this, it would be nice to use iGPU only for PC GUI.

I hope someone understand this situation and have a solution.