Switch Between NVR Sites

I have a client that has a few retail stores and they are looking for a better NVR/Security experience. Currently they have an off the shelf NVR/camera setup at each site. This become difficult to manage and asked if there was a better way.

I was hoping for a Unifi type experience, with 1 app, 1 login, and easy enough to change sites. Ideally they would keep their existing cameras, and just replace the NVR at each site?

I know this is an odd use case, and likley not many options short of ripping everything out, but thought I would ask.

Looks like Eagle Eye and Verkada require you to use their cameras?

Thanks for any help!

Synology has something to go with their storage, or look at Shinobi or Frigate if you want to roll your own.

Assuming that the cameras all stream over ethernet, then any of those 3 should work. I’m looking into both Shinobi and Frigate for possible use at home, I have a GW Security system with their NVR, but think I may want to move to Frigate. The GW cameras are good, at least all the ones I’ve used, and GW support was very helpful when I burned out a connector from water leakage. After explaining what I did for a living, they agreed to warranty me just the cable whip so I could replace the burned connector, it was around a 15 minute job to open the camera and change this cable. May not be the cheapest cameras, but I can’t fault their support.

Anyone reading this and thinking to buy a bunch of GW stuff, look around the web for systems, you can normally source the cameras and NVR for less than just buying the cameras.