@meatballs I can see the attraction of wiring, but the ESP32 in the proposed M5StickC [Plus|Plus2] doesn’t do Ethernet, only Wifi. It’s also powered from the X10M serial port socket, so that’s not an issue.
This post Send Shelly data to emoncms explains how to script a Shelly Pro/Gen2+ device to send data to EmonCMS (local or cloud) via HTTP. So that removes one MQTT requirement.
I totally get the maintenance problem for Wifi, in respect of AP/WPA configuration changes, for both Shelly (requires accessing the device, possibly in AP mode if wifi changed) and ESPAltherma (currently requires text edit and recompilation!). Not much you can do about that, unless you’re prepared to write/test ESP32 code - there are libraries that handle web-based WiFi config, but would need integration into existing code.
The bottom line is that it’s complicated, reliability is non-trivial, and that’s probably why solutions are either expensive, or require lots of user input as a substitute for cash!