Programmer Humor

You need electrical experience, I wouldn't recommend anyone to work with high voltages unless they knew what they were doing. The method depends on the device, every one is different. For the aircon unit the esp is an internal remote, so I spent time decoding that model's IR codes and building a platform for reliable control via home assistant. I have fans around the house that use mains voltage motors with 3 speeds, those got an interlocked 3 channel relay board. The ice maker used digital logic, so the esp sits between the control board and the rest and intercepts button presses to keep track of state and the injects its own commands for remote control(not my work). If you are lucky there will be a guide on the internet you can apply to your specific device, otherwise you'll have to work the project out solo from smaller guides.