Like marmite people either love the Samsung Cycle alarm / cycle completition tune or hate it. Here is how to turn it off on the 2020 slimline control panel.
Turn the washer / dryer on.
Hold down the more functions button down for around 5 seconds.
This menu will appear, turn the wheel until you get to alarm
This should be the second option, as shown below.
Tap the O to turn it off:
Turn the wheel to the back option and press O
The machine will exit back to the main menu.