Private security footage is nothing new to criminal investigations, but two factors are rapidly changing the landscape: huge growth in the number of devices with cameras, and the fact that footage usually lands in a cloud server, rather than on a tape.
When a third party maintains the footage on the cloud, it gives police the ability to seek the images directly from the storage company, rather than from the resident or business owner who controls the recording device. In 2022, the Ring security company, owned by Amazon, admitted that it had provided audio and video from customer doorbells to police without user consent at least 11 times. The company cited “exigent circumstances.”
For “commercial but free” There is AxxonOne (was AxxonNext) But free only allows 4 cameras. However this is better than all the FOSS choices in terms of what it can do (and so it should, more than 4 cameras or face detection, fire etc costs money).
For FOSS there is:
Lots of options but you will need some baremetal or a decently powered server and hypervisor to run in a VM.
Set up two 4 cameras