Just because there's an app available doesn't necessarily mean it's required. It might be that other solutions just haven't been typed out in their docs.
I've recently worked with some of D-Links consumer IP cameras, DCS-8302LH and DCS-8000LHV2. They offer an app and optionally cloud storage but they ship with ONVIF support. No web interface afaik, but what I found was that I just needed to start interacting through ONVIF to get going with a local-only setup (this would automatically disconnect the camera from the app as well).
These cameras are some of the cheapest available, but they have been solid.
I've recently worked with some of D-Links consumer IP cameras, DCS-8302LH and DCS-8000LHV2. They offer an app and optionally cloud storage but they ship with ONVIF support. No web interface afaik, but what I found was that I just needed to start interacting through ONVIF to get going with a local-only setup (this would automatically disconnect the camera from the app as well).
These cameras are some of the cheapest available, but they have been solid.