Unknown device on new wifi network set up yesterday

This ethernet MAC address does lead to the Organizational Unique Identifier (OUI) for Qool Tech Industries.  What a mystery!  I agree entirely.  Without the password, a device cannot connect.

The device "type" that Orbi assigns to something is somewhat of a wild guess.  "Computer" might simply be the default for "I have no idea."

I am not a big fan of the Orbi "app", and have never activated Disney Circle (no kids).  On the Orbi web interface, the Advanced Tab->Security->Access Control provides a way to control which devices can attach to the network.  If you scroll down the page, there is a table at the bottom of MAC addresses that are blocked from access.  Note that when Access Control is activated, there is also a choice about whether new devices are allowed to connect or not.  This is a "double edged sword" sort of thing.  If Access Control is activated and new devices are prevented, then every time you want to connect something, you have to go back to the Orbi web interface and allow it.  i.e. Your wife's sister comes over while you are away at work and wants to show some things on her iPad.  The wife says, "oh, our WiFi password is xxxxx", but she can't connect.  For myself, I err on the side of, "if it knows the password, it can connect until I decide to block it."

Maybe someone will offer an explanation?