I have a few Reolink POE cameras(and poe doorbell) with an old mini pc running frigate, all on a battery backup so if the power goes for a bit the cameras and recording don't. I also have a coral tpu installed in the mini pc.
All of my cameras are blocked at the firewall from leaving the network and they function fully, 100% local. When i plugged in the poe cable the cameras grabbed an ip address and you can interact with them through that.
As others have said there is also a home assistant integration for reolink that let's you import and control the cameras from within home assistant as well as a frigate integration. I prefer having frigate on it's own box so when i need to reboot home assistant my cameras are still recording.
Once it's all set up you can have live video feed for each camera accessible within home assistant, on your dashboard if you like, as well as access to clips and continuous recordings depending on frigate configuration and storage capacity.
I've lost count of the number of times and number of formats in which i've consumed The Hitchhiker's Guide to the Galaxy and i've loved it every time.