A WiFi unit that comes with an optional USB Ethernet port for $14. Would never buy a WiFi unit only after the last one and trying to set it up with DNS entries. The Fire TV box is way easier. Hope this one is easy as well ..
Old ones are fine with custom dns on wifi. Not sure what problems you have but was the same as ethernet for the fire tv when I did it other than having to choose the network and key.
With the Wi-Fi version you have to delete the Wi-Fi account and then create it again with the new DNS entries but with the ethernet version it's just change the DNS entry.