Ok there are basically 3 kinds of switch and a few different antennas
NOT ALL Have a switch but on a 2018 I'd be very surprised if it did not
Type one is the good old wall plate. Light, Switch, 12 volt outlet
A variation on that is a wall plate with TWO digital displays and a row of LED's between them it has 3 buttons the top button is the switch
Next is a wall plate with a switch, and in fact this can be any kind of switch and need not be on a wall plate either ...
My OEM was a Box of Many buttons (Technicial name matrix switch Winegard calls it a Video switch or Antenna switch)
If you can not find it... Turn off all 12 volt Disconnect cable from antenna head (If visible) hook up a cable tracker from Harbor Freight and beep beep beep your way to knowledge.. NOTE Very handy device!!!!! It has found several things for me.