If you are using a built in PoE ports on the back of the NVR then that would be an issue since all cameras would be on it own separate subnet which would not be visible to Scrypted on a Pi. Unless the NVR have a setting to put camera on the same subnet as the NVR is on itself.
I also have Dahua NVR and I only got the 1 port version and I use a separate PoE switch to expose all my cameras to my home network to other applications like home automation, or 3rd party security camera application etc. I used to run an app on FireTV that allow me to quickly bring up all my cameras on TV with a press of a button on my FireTV remote which now I have switched over to Scrypted and AppleTV.
If your NVR is the PoE version then yeah you'll need to get a PoE switch and move all the cameras over to your home network or on the same subnet that Pi and Apple hub will be on.