> An IoT device actually monitoring mains (and only that) seems like a better solution This is what I was thinking. Specifically I have several different model

> An IoT device actually monitoring mains (and only that) seems like a better solution This is what I was thinking. Specifically I have several different models of Zigbee and Z-wave "smart outlets" among the myriad IoT devices I've evaluated. While reading through the OP, I found myself wondering if one of them could just be left in the "ON" state, powering nothing (or something I always want running like a freezer). Then I could simply have HomeAssistant, which is backed by a UPS along with my modem and router, report its status.