Diagnosis
Absolutely, you can. The Ethernet port on the ZenWiFi node is a standard LAN port. You just need to be mindful of how you connect it.
How to Fix It
It's straightforward. 1) Get any unmanaged network switch (5-port is common). 2) Plug one end of an Ethernet cable into the LAN port on your XT8 node. 3) Plug the other end into any port on the switch. 4) Now you can plug your computer, printer, game console, etc., into the other ports on the switch. The node will handle assigning IP addresses to all those devices.
If That Didn't Work
If devices plugged into the switch don't get an internet connection, the cable might be bad. Try a different cable between the node and the switch. Also, make sure you're plugging into the node's LAN port, not the WAN port (the WAN port is only used on the main router node to connect to your modem).
Heads Up
Don't create a loop. Never connect two ports on the same switch together with a cable, and never connect a node back to the main router or another node with two separate Ethernet cables. One cable from node to switch is all you need.