Single PoE switch with cameras on a VLAN (so they don't have internet access). I use my old framework main board (yay for reuse!). Started with a USB Coral but switched to NVMe, which is more reliable passing through to a VM.
Last time I looked at this the Coral devices were out of stock and price gouged. Looks like I can at least order now with a lead time of 22 weeks from mouser.
No worries. I picked up some nvme to make a low power frigate box when I saw the USB is often unobtainium. Figuring out the whole m.2 keying scheme vs the ports I have took the longest of it.
I found that one key type is for wifi daughter cards so I was able to save a pcie slot or nvme slot using that in the small form factor host.
Frigate links some Dahua camera recommendations in their documentation: https://docs.frigate.video/frigate/hardware/
I installed them and they've been rock solid. Low light performance is excellent. The turret form factor is nice and unobtrusive.