Not as high tech as other answers, but I configured some months ago 2 rpi3 with picameras.
I'm running mediamtx on the Pis in order to do rtsp.
I have motioneye configured for motion detection, saving videos and sending telegram messages (But the project is dead and I'll probably look at frigate to replace it)
Trilium is nice as an obsidian alternative
Not as high tech as other answers, but I configured some months ago 2 rpi3 with picameras. I'm running mediamtx on the Pis in order to do rtsp. I have motioneye configured for motion detection, saving videos and sending telegram messages (But the project is dead and I'll probably look at frigate to replace it)