It depends upon what you mean by "NVR". If you just want to save video from a lot of cams, you can do that! I have 8 Amcrest cams saving to my DNS-323 via ftp. The DNS is capable of storing many such streams. But it's not doing any processing of the data, such as detecting motion, sending email notifications, etc. With my cams, all the motion detection is done by the individual cam, then when motion is detected, the cam simply saves the video file to the DNS. What you are left with are organized subdirectories of daily/hourly sets of saved video files that you can play with any .mp4 player. That's probably the best way to go, rather than having an NVR process motion detection, which have limited CPUs, and even standalone NVRs can't process that many motion detection streams at one time. The DNS does what it does best - storing files, and the cam does what it does best - detecting motion.
However, this does not provide you with a video package for managing the software or play multiple streams synchronized in time. Most of those config screens you see in the DNS app are just wrappers for things you can set up on the individual cameras themselves via their own interfaces instead of using something like the DNS app. For displaying multiple cam footage in real time, I use Amcrest's own surveillance software, and your cam maker most likely has something similar - it's pretty standard stuff. You don't need special NVR software to do that.
HTH.
-Cosmo