There's probably a connection in the closet. The cableTV/antenna coax connector and satellite coax connector come out on one wall plate, with a jumper to a 2nd wall plate having a single coax connector. You could put the cable set top box there and connect the output to the single coax wall plate which in turn connects to the back of the TV.
If the cable company is also putting in a cable modem with WiFi, it could also be placed there and your various devices would connect to it via WiFi, not hard wires.
But, if you have a TV that doesn't have WiFi capability, but rather has an ethernet connection for "smart" functions, you'll be on your own to add an ethernet connection.
As for the TV mount, sometimes the TVs are hung on a wall bracket and 1 or 2 screws accessed from the bottom hold it tight against the bracket.