Miracast does not work over wired Ethernet. It uses Wi-Fi Direct. Your laptop must have a WiFi adapter. Bluetooth is irrelevant. Your router is also irrelevant.
Please read my OP(s) again. It was the Bluetooth failure that lead me to try Miracast instead. Then, Miracast appeared to have an IP address conflict, and I discovered I could not find a way to log into my router (likely because it is behind a switch.)
I am pretty dumb on this stuff, but I am WELL aware Bluetooth and Miracast are separate and distinct systems, and Bluetooth does not utilize WiFi.
I have also stated the WiFi on the laptop was otherwise working fine.