How do I get the cover off my Samsung over the stove microwave? Do I have to take it off the brackets?

It likely depends on the model. To access the circuit board behind the numeric display, do the following. On the SMH9187ST model (and probalby most models that have the numeric display to the right of the door), you remove the top vent guard that runs across the top front of the microwave. There are 2 screws holding it in. Open the door and then slide the panel 1/2" one direction then it will lift off. Remove the center and right screws on the bottom of the cabinet, directly under the door. Remove the single screw at the top of the numeric display and the display and circuit board will lift free of the cabinet. The connecting wires can each be removed as there is only place they will each attach to when it's time to reconnect. Some are color-coded, others have unique connectors.

Samsung microwaves seem to have a high occurrence of the SE error code. This happens when the edge connector on the ribbon cable gets oxidized from steam that enters the cabinet through the seam at the numeric display and the cabinet itself. You can often remove and clean the edge connector with alcohol and buy some time but it will happen again. Replacing the circuit board is the next step after the cleanings stop working. Places like partsimple.com stock both the display and the board.