I’m on the bandwagon of no “smart home” devices that connect to the cloud. I build a lot my own little controllers with the ESP8266/ESP32 using MQTT to communicate with OpenHAB.
OpenHAB has served me well, but I started using it so long ago that I have not tried out some of the newer options like HomeAssistant.
The code referenced in the Instructable is much older code. I don’t think I have my current and much simpler code on Github. If there is any interest, I can push it.
HomeAssistant has been around almost as long as OpenHAB (2013 vs. 2010), so it's not exactly "newer". It's good that there are several open source options, but I don't see anything wrong with sticking with what works for you (OpenHAB for me as well, btw).