I know you said Open Source but the ones I tried were not fabulous. I used BlueIris for about a decade. I recently depreciated that for a Ubiquity NVR and cameras. BlueIris works well if you have an Intel CPU with iGPU to do the decoding. BlueIris can record to network attached storage and if you follow online guidelines you can ensure CPU utilization isn’t through the roof.
Honestly, I get where you’re coming from but look at it through this lens. Sometimes photos can be painful, like seeing your future ex wife who you are going through a messy divorce with. Additionally, what if a relative just passed away and you’re having a hard time about it? I can see this feature being useful.