It is what I have been doing for more than a year. It is not difficult but does require some familiarity with network configuration and a bit of hardware hacking if you want to use ESPHome or Tasmota or something like that. I use this to control the solar inverter and a number of appliances. I also read the power meter using a homebuilt reader (which is where the hardware hacking comes in) which I use to control the output of the inverter based on momentary power prices (we have hourly rates and can sell power at market price which also implies we show not send any power if the price happens to go negative).
In other words this is quite doable for those who have some experience in setting up networked equipment. It is not something you'll tell your grandma to do but there is nothing keeping you from setting it up for her since it is a one-time job. It is also more than worth it for the gains in privacy, the reduction in exposure to exploits and the absence of the risks of automatic updates which take away functionality you depend on.
In other words this is quite doable for those who have some experience in setting up networked equipment. It is not something you'll tell your grandma to do but there is nothing keeping you from setting it up for her since it is a one-time job. It is also more than worth it for the gains in privacy, the reduction in exposure to exploits and the absence of the risks of automatic updates which take away functionality you depend on.