Those Shelly diagrams are confusing because it’s not clear that the diagram is the external connections. I’m used to seeing it the other way-

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The SW looks an awful lot like a relay contact that is internally connected to line. Little harm wiring that wrong.

Here’s how it should be visualized

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That O terminal looks like a coil that needs a L connection to energize it cause the other side is already connected to N, let’s put some power to it through my switch!

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