As others have said, Home Assistant is a great option, built from the ground up to be both completely local and private if you want, as well as extremely flexible. My entire house runs mostly on zwave and zigbee for lighting, security, power monitoring, hvac, cameras, and sensors, and those are kept completely local, no clouds, no companies, all running on a mini pc in my closet. Plus it’s able to connect to other existing cloud stuff to integrate that don’t have a local option, such as smart TVs, car chargers, smart thermostats, anything you can dream. r/homeassistant and their home-assistant.io are good starting places