I work for a multi-national IT department. I just happen to have a UK, FR and DE laptop on the workbench. I don’t see the em-dash on any of them. AltGr + hyphen does nothing on Windows (Google search says Mac supports this). None of these laptops have a numpad, but Google search says maybe CTRL+MINUS(numpad) may give an em-dash. Can’t test though.
In any case, it seems the world has left behind em-dash, so correcting users on a public forum seems pointless.
Okay yea sorry, the sarcasm was whooshed on me.