I've never seen a build-your-own solution be easier than "Register Here/Get Started".
Build-your-own?
A smart-home-controller is a physical device. You buy it, you provide power and connect ethernet and configure wifi. Now, either the controller relies on the cloud or it doesn't.
If it is completely reliant on the cloud you will have to muck about with registering, if it is completely self-hosted you don't. Simple as that.
You still need to connect the power cord and connect to ethernet or wifi (end regardless of whether it is a cloud device or self-hosted device you can configure wifi from your smartphone like the chromecast).