I have recently discovered this very useful Homeyscript (thanks to @Sharkys and @Caseda):
Put this in a flow that is executed regularly, and it returns a tag telling you how many Zigbee devices have been offline for two hours or more (it also returns the names of the offline devices in another tag). In my experience, Zigbee devices seems to poll at least once each hour, regardless of whether anything has changed or not. If you take a look at your Zigbee devices in the Developer Tools, you’ll see there is a column called “Last seen”, and it is this value that is checked with the linked script. For my devices, I’ve never seen this value get higher than 1 hour (unless the device is truly offline).
You can of course modify the script however you want, you can edit it to have a different time limit than 2 hours, although that is probably a reasonable value to use. I think this only works on the Homey 2023, but I might be wrong.
I do agree that Athom should have added some official means of getting this information, but as of now, that doesn’t exist (to the best of my knowledge).
