I’m working on something that you could use to build one out of a raspberry pi. Or an old laptop. Or a mini pc and webcam. Basically anything that runs Linux and has a camera.
https://github.com/sciactive/soteria
It uploads video to a WebDAV server. I’m designing it to work well with my WebDAV server, Nephele. Nephele supports encryption at rest and Amazon S3 compatible servers.
It’s not going to be as feature rich as other solutions, but it’s killer feature is that you can watch your footage even if all of your cameras are offline, but Amazon/Google/whoever can’t ever watch your footage.