I really wanted to repurpose my old phone as a security camera , but android power management and lack of sensible way to automatically restart the app for an IP camera made it not very practical.

this could be a promising project but device support looks very lacking at this moment.

I also considered postmarketos but AFAIR for my particular phone it didn't support the camera, so I stuck with rooted android with some hacks to slow/pause battery charging (it is holding about 5min anyways)