Netflix's dvd rental service is just as great as his VOD video service. If you want to save the contents inside the disc you borrowed from Neflix for your permanent collection, then you need to know what the disc's copy guard is and the tools that can unlock it, there are many free tools that can do it.
Also, there seems to be a lot of paid software that can even unlock the DRM protection in Nexflix's VOD service now.
[1] https://disc-keep.com/introduction-of-disc-copy-protection/
[2] https://dvdripper.cc/download-netflix-videos-permanently-with-streamfab
