Hot water heater? Yes, I did find it.
I specifically bought a Rheem ("Performance Platinum" model) last year because I can control it with Esphome.
Little M5Stack Atom controller with rs485 module plugs right into the port on the water heater, using a simple old-school modular phone cord. I do not use the water heater's wifi or Rheem account/cloud service.
It works great completely local from HA. I automated it to boost the thermostat setting extra high during lower electricity rate time of day, and lower the thermostat during peak billing time. So I can bank extra stored heat, for less cost.
I added a thermostatic mixing valve on output, to ensure regulated safe temperature to pipes and fixtures.