There are hundreds of different NVR solutions out there. The consumer ones are... meh. But they mostly work.
The reality is that except for companies, almost no one REALLY cares about it. It's an expense they'd usually rather not have (like backups), so it always gets the short end of the stick.
It needs to be basically the same as a Ring with just one additional requirement, plugging another box into power and your network to act as the DVR/brains, with a QR code that you scan to link it. Sure that can have more customization options, but the default has to be zero config. Probably gonna need a cloud server for notifying and serving the mobile app without having keys to the video, which would cost money monthly.