In Switzerland, you (almost) always need at least one T12 (3-pole)->Schuko adaptor for a Shelly Plus Plug S, e.g. a Max Hauri Fixadapter 135800 (black) (Digitec 5857871). If the end device is T12 3pin or T23, you need a second (different) adapter; if the end device is T11 2pin or Europlug, you do not need a second adapter. No adapters are included.
Yes, it needs an adapter at the front and at the back, and no, they are not included. Otherwise, however, the thing works well. I simply cut off one end of one of the dozens of cables with Schuko plugs from other devices and attached a CH connector. It's cheaper, you have an extension cable and it makes the Shelly a bit more compact.