When I went through this vueville had enough info for me to build an intuition for what to look for on Amazon.

https://www.vueville.com/home-security/cctv/ip-cameras/ultim...

No actual links, but ReoLink PoE cameras, a miniPC, PoE switch, Zoneminder, 2TB SSD, external enclosure, and backup UPS.

A more contemporary alternative to ZoneMinder would be Shinobi: https://shinobi.video/

How have you found Shinobi versus Zoneminder? I've been using ZoneMinder for years. It's a bit clunky but once it's set up it works fairly well, but I'd be open to switching to something better.

Looking at their assorted instructions I see some pre-canned methods that assume a specific OS. I can't find detailed instructions for people that already have Node, FFmpeg and MariaDB installed. Is that on a forum?

Reolink cameras are pretty affordable, can be accessed with ONVIF, and you can just put them on a VLAN/Firewall that has no internet access if you're afraid that it's phoning home.

I have a Synology NAS and their free security camera software is pretty easy to set-up and use with ONVIF cameras.

POE cameras paired with either an NVR or custom server. I prefer wired cameras and local storage.

If you want a really simple, dumb, and cheap local storage camera check out Wyze. By "simple" I don't mean "hacker news simple" but actual "normal people simple". Just be sure to disable the cloud upload option after installing an SD card: https://www.wyze.com/products/wyze-cam

The cameras are nothing special, but great for the price point. They support locally writing all video or just motion to an installed SD card. By default they'll upload 10 seconds of motion to the cloud but you can disable that. Or to be really sure, after setting up the SD card you can deprive it of internet access (block it or remove the wifi SSID you used for setup), and then you can be very confident it's not uploading anything. With this approach you'll need to physically take out the SD card to access the video.

There's certainly better local storage options out there. But for a single camera it's a pretty dead simple local storage setup.

"you can deprive it of internet access".

Very good advice when it comes to Wyze products. Sadly they're just the tip of the security/privacy nightmare iceberg.

I am using Frigate. Simple, open source project. It streams the cameras and can do object and motion detection and only record for specific events (like motion). It allows me to set how long to keep the recordings. For any additional functionality, I have it integrated with my home assistant.