See if rebooting your router and doing a System Restart of your Roku device solves it for you. (Settings..System..System restart)
When your router reboots and after you do a System Restart, see if all networks are again available. You may have to press SCAN AGAIN under the Network Settings to make visible.
Since no option showing for wired, one of these steps should work for you. You can also try using another ethernet port on your router. If not, post back with your Roku device model and router model.
Although does not explain why Wired isn't showing as an option, the 5gz settings may have changed to either a protocol excluding the 5gz capability of the Roku, or switched to a channel not recognized by the Roku forcing it to use the 2.4gz. Post back if restarting router now gives you access back to both bands.
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