Here's what I did for humidifiers in my house:
- Dumb, analog-controlled humidifiers (like with the knobs, no digital displays, buttons, modes, etc)
- Local control smart plug (Tasmota flashed Sonoff S31 in my case, but it can be anything)
- Humidity sensor (I use the Zigbee Aqara ones)
- Create a Generic Hygrostat entity
Now you've got a smart humidifier in Home Assistant. You can set the desired humidity, and when the sensor detects it's below this, it'll kick on the smart switch. When it passes the threshold, it'll turn off. It's been great! My humidifiers shut off when the water level drops, so I can even use the power monitoring in the Sonoff switch to send me a "low water" alert when the humidifier should be running, but it's drawing no power!