Neat project, but this implies some sort of ongoing third party dependency/control that the devices would have, making it a non-starter for my use. The main reason I am using RPis as security cameras (for one use) is to avoid these type of security vulnerabilities.
There's OpenBalena for hosting your own device deployment and management server. https://www.balena.io/open/
It's self-hosted, which is a double-edged sword. You have to setup and maintain your own infrastructure, but you don't depend on a third party. For personal projects, it's probably the way to go.
Additionally, devices can be moved between servers easily. If you decide to use the cloud hosted platform in the future, or move devices from cloud hosted to self-hosted, it's easy to do.
Just to let you know, this is the approach that balenaOS takes. Applications are containerized and deployed using Docker. The OS uses read-only system partitions to store the engine, kernel, firmware, etc, and has an A/B partition layout for resiliency and atomic updates. Applications are downloaded and stored on a separate data partition, and mutable configs are stored on another. The partition layout and a lot of how the OS functions is also well documented and public. [0]
Additionally, the first ten devices are free and fully featured, and the same people that help create the product, including (but not limited to) engineers, monitor the forums to help users. I'm one of those engineers. :)
[0]: https://www.balena.io/docs/learn/more/masterclasses/host-os-...