Why are there multiple devices with the same name listed in the Client List?

A MAC address is a unique network address for a device to identify itself to the network. When a device with an unknown MAC address joins the network, the network will identify it as a new device and then list it in the Client List.

To further protect user privacy, iOS 14, Android 10, and later versions have released a new feature called Private Address. Devices of these versions can use a different MAC address with each WiFi network, and this unique, static MAC address is the device's private WiFi address for that network only.

Since Private Address is enabled by default, each time the device joins different networks (including different bands), it will be identified as a new device and listed in the Client List with a different MAC address.

It is safer for a device to connect to a public WiFi using a Private Address. However, in-home networks, some features like Parental Controls, QoS, and Blocked Devices are implemented based on MAC address, so if a device is using a private address, don’t forget to add it to the controlled list. Or you can also disable the Private Address feature on your clients following the instructions:

iOS14:  Setting -> WLAN -> tap on the blue info icon at the left of the deco wifi name -> disable the Private Address feature. 

(Picture refer to https://support.apple.com/en-us/HT211227 _

Android: Settings app -> Network and Internet -> WiFi ->Connect to deco wifi -> Tap the gear icon next to the current wifi connection -> Advanced ->  Privacy -> "Use device MAC"

Window 10: Setting -> Network and Internet -> "WiFi" tab -> "Advanced Options." -> "Off" under "Random Hardware Address."  -> Restart your computer. 

(Picture refer to https://it.nmu.edu/docs/disable-random-hardware-address-windows-10 )