I have a mixed setup with Ikea Tradfri, Shelly’s, Zigbee2MQTT (mainly Xiaomi) and RFLink (433 mHz).
A couple of the Tradfri lights are on a wall switch, and get switched off regularly (by the wife and kids). As you probably know, this is a problem, because HA does not detect this.
I was wondering if a gizmo exists that you can connect (in parallel) to a tradfri light, battery powered of course, that changes state when the wall switch is turned off (i.e. when it loses power). It could connect to HA as a Zigbee or wifi device (or even 433 mHz?).
I know you can detect the availability by polling the light regularly, but this type of hardware sensor would make the detection almost instant.