What smarthome ecosystem is most open, private, and hackable?

As the title suggests.

I walked into a Home Depot yesterday to buy a lightbulb, and was overwhelmed by all the "smart" bulbs with different smarthome service names.

Yes, I do want a "smart" bulb. I want to be able to write some python that can control all the lights in my house.

But I'm wary of anything that needs a round-trip across the internet to turn on my reading lamp. I just want a local network of devices that I can easily control, without fear that a firmware update next month will close them off.