

Switch mode is set to ‘Follow’. I do see now that the page is showing the input as ‘OFF’ where previously it wasn’t changing from ‘ON.’ Perhaps some leaking current or a massive delay.
More testing tomorrow!
Edit: Current leak confirmed. :( Randomly went back to ON and switched it on. But at least I know it’s not a Shelly issue?
I have an Aqara FP-2 doing just this thing. It works pretty well after setting up zones. Those get pulled into Home Assistant and then you can tie those to automations to control lamps or what have you.