I succeeded in blocking a couple of unknown devices on my network using the app as follows.
You can't put a 24 hr block on, i.e. from 0:00 to 0:00, the best you can do is 23H 59m which I did for each one of the devices individually. I then created my own group with different start and end times to those I set on the devices so that they overlapped and dumped each of the devices to block into there.
I could see from the event log that each of the devices that I blocked could still issue a DHCP request, received an IP address and was able to connect to the router but none of them could communicate either with the internet or with any other network device and disconnected again after just a few seconds.
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