On my (old) Connect Box (gigabox?) , in the “home” page I can click on the names (default “unknown”) and select the type of device (from a very limited list - and it does nothing apart from change the icon) and type the name.
In my (old) box, the DHCP settings take the device name from the above; there’s no way to change it there.
I can enter names under Security/MAC filtering, but I’m not sure if that gets reflected in the connected devices area. You could always try that, and just ensure “enabled” isn’t selected once the device is added to that list.