Try going to Settings and search for Maintenance mode. Otherwise it should be under Battery and device care > scroll all the way down > Maintenance mode.
I am very sorry to hear that the steps provided aren't showing you Maintenance Mode, as those are indeed the correct steps. Although an Australian link, this will show the pictures of what SHOULD be seen when attempting the steps, assuming you are on the latest Android version: https://www.samsung.com/au/support/mobile-devices/activate-maintenance-mode/
If that is not what you are seeing, can you provide screenshots and/or tell us what you are seeing on your end following them?
