ONVIF is the (now quite old, but still very relevant) standard for interfacing IP cameras locally on a network.
A cheap-but-performant ONVIF camera on an isolated VLAN (or a physically-isolated network; I won't tell anyone) can be a thing of beauty that is also completely unable to call home to some mothership in the clown.
I'm frankly very surprised that I don't see it mentioned here more often when discussions of cameras arise.
ONVIF can be used to discover a camera on a network, query it for its RTSP URL, and facilitate a connection between a client service and the RTSP stream. But you can't stream video via "ONVIF".