Push2Run - Push2Run is a free program for Windows which lets you to control your PC or laptop using your Google Home, Google Mini, Google Max or smart phone running Google Assistant.
FHEM - FHEM (TM) is a GPL'd perl server for house automation.
SmartThings - SmartThings makes it easy to turn your home into a smart home.
Conrad Connect - Service for managing smart home devices
Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
pimatic - Home automation framework that runs on node.js.