@DREEMus 

This has to do with the client device. Not all clients broadcast their network ID properly. In those cases you may have a hostname set, but the device doesn't broadcast it as the network id. Omada is configured to list the device by it's mac for its name in those cases. It would be nice if it used the hostname for that, but not all devices broadcast the hostname either. This mostly applies to wireless devices as wired devices normally broadcast the hostname as the network ID. Though some wired devices do let you set a network id different then the host name.

It's because there isn't a real DNS server built into omada. It does not have the logic, if you will, to read the device hostname just the broadcast device ID. If that is not configured by the device, omada doesn't know what it should be and just assigns the make as the device name. Lots of devices set the device id for the nic to be the same as the hostname, but lots do not. This is a known issue with omada. This is most commonly an issue with wifi devices. As far as omada goes, this field give you the option for a "sudo dns", though it only works for record keeping and in no way functions as real DNS. It just lets you set a friendly name for devices that it isn't smart enough to figure out the hostname for, while defaulting to the mac so you can find out what device it is.  The field should still display the device mac in the clients list, that is at least how it works for me. Maybe you cleared it on accident?