Setup a LAN with PoE and use whatever crappy PoE cameras are the current cheapness. Bonus if you find confirmation they zonemind.

Block that entire lan from accessing the Internet after its setup. If you need to get video out, use a bastion host to do so.

Homeassistant was able to make the cameras work with HomeKit somehow but i forget the details.

(For most of them I just RTSP direct with a password in VLC, and internal website links to them all and it works well enough for quick checks. You can make playlist, too)