Recording is local and needs no internet
The recorder (NVR or DVR) receives the image from the cameras and saves it to a disk inside itself, whether there is internet or not. Even if the internet is down for a whole week, your recording continues and is kept in full. The internet has nothing to do with the act of recording.
Local viewing without internet
You can watch the cameras directly on a screen connected to the recorder, or from a phone or device on the same local network (the same router) through the app — all without internet. The local network is enough for viewing inside the site.
What actually needs the internet?
One thing: remote viewing — opening your cameras from your phone while you are outside the building or in another city. That needs internet at the camera site so the stream can reach you. If you do not need to see them from outside, you do not need internet at all.
Options if there is no fixed internet
For a site without fixed internet (a farm, a distant warehouse, a construction site) there are options: a data SIM (4G/5G) in a small router is enough for remote viewing, or you rely on local recording and review it on a visit. We choose what suits your need for remote access and its cost.
In short
Cameras work and record perfectly well without internet. Ask yourself one question: do I need to see them while I am away? If yes, you need internet (or a data SIM) at the site. If not, a fully local system is enough and records safely.