Energy metering / smart metering

Are there any known alternatives that can run on something simpler than a RPi? I was thinking about a Esp32 device for instance, that could be something more IoT oriented than a RPi imo.
If not, I’ve got one or two PI 2 here.

First thing that comes to my mind when talking about ESPs is Tasmota. But you’d have to provide your own Smart Meter script.