U4025QW, DDM network KVM to make two PCs connect to each other

Hi 

I have a Dell XPS 13 and a U4025QW as my main setup and another old Dell laptop with a non-Dell monitor in another room. I only use this other PC to help my son edit YouTube videos as it has all his editing software on there. I was under the impression that with my U4025QW, I could use the DDM (Dell Display Manager) network KVM functionality to connect the XPS 13 to the other PC?

I have installed DDM (latest version) on both PCs and checked the boxes to enable network KVM/support file transfers. It works fine on my XPS 13 but on the other Dell PC, it complains there isn't a Dell monitor attached. I get that it would do this in terms of using the monitor setup functionality but I thought this would enable my XPS 13 to connect to this other PC?

If I ignore that and go to add the remote PC from my XPS 13, it doesn't find it, even though DDM is running on the remote PC. I've tried scanning and connecting by IP address and it just says the PC isn't found.

Surely the other remote PC doesn't also have to have a compatible Dell monitor on it does it? I wouldn't even be using that monitor, that's the point of connecting to it remotely using the network KVM. 

Can anyone tell me if I need a Dell monitor on the remote PC or if there is some other reason it wouldn't connect? If it needs a KVM compatible monitor on the remote PC that essentially makes this useless for me.

Thanks in advance.