PacDDrake

Hello everyone,
some quick context for my Issue that will hopefully clear up any possible misunderstandings:
 
For my birthday (which happens to be today), I decided to upgrade my gaming/development machine with some new hardware.
At the same time I decided to try and switch to Linux as my main operating system since it just feels nicer compared to Windows 10 for me.
Also, Proton has made gaming on Linux a much more pleasing experience by now since almost all of my games now run with great performance.
Still, for the few games I have that will not run with Proton or Wine I decided to use Windows and just run it in a VM so I don't need to switch OSs every time I decide to have a quick match.
 
Long story short, my machine now has 2 NVIDIA GPUs: GTX 770 and GTX 1070 Mini
running on a new Gigabyte X570 Aorus Elite with a Ryzen 7 3700X.
The GTX 1070 is intended for any heavy lifting purposes, such as gaming, and thus has my 2 big 1440p monitors attached to it,
while the GTX 770 is merely intended for output of the host system in case I run any VMs with GPU-passthrough, which is a can of worms I decided to open at a later date.
 
My current Issue is that, even though all hardware, both GPUs and all 3 on my monitors are confirmed working,
but any display attached to the secondary GTX 770 GPU shows no output and is not shown as a possible output device in the display manager:

However, both the secondary GPU as well as the attached 1080p horizontal monitor are recognized by nvidia-settings as existing and theoretically working: (GPU 1, HDMI-0)
I have googled a lot this past day, but most issues I came across are with hybrid mode for GPU and CPU-onboard graphics.
 
If anyone has a solution for my Issue to get the third monitor on my secondary GPU working, it'd be the best birthday gift I could ask for.
 
Sincerely, PacDDrake
 
Quick Update: I have managed to enable the tertiary monitor by creating a new X Screen for it in the nvidia-settings:

It now shows output. has the correct resolution and orientation and I can now move my mouse into it.
However, I only get a black screen (no wallpaper like on the others), the cursor immediately changes to a black X and I cannot drag any applications into the screen.
Any help on getting application output, even if they then cannot be dragged between the different X Servers would be much appreciated.