[losvedir]

It's just Option + dash. Using option as a modifier is second nature if you ever write other than English and need, eg, é or ñ or something.

[jandy]

Fwiw, that’s actually an En dash not an Em dash. You need a Shift in there to get an Em dash.

[latexr]

It depends on the keyboard layout. Some (US) do have it like you described, but others have the dashes reversed.

Both make sense, to a degree. On the one hand you can argue that the em-dash—being longer—should require and extra key, but on the other hand it has more uses so it should not have the extra key to be more accessible.

[jandy]

Ah I hadn’t considered keyboard layouts.