I have a Mac (and am very familiar with all its nifty shortcuts) but also a Windows and Linux machine, how would one type it on those?

To enter an em dash on Windows, hold down Alt and type 0 1 5 1 on your keyboard’s numpad. (Alt 0 1 5 0 for an en dash.) This only works with numpad number keys so laptop users are out of luck.

It is insane that in 2025, this is an accepted way to type lesser-used characters on Windows still, when the Mac has had the Option key typing umlauts and em-dashes extremely simply (an umlauted U is literally option-u, u... Ironically, I'm currently on a Windows machine so I cannot even type it) literally since 1984.

My family is German (I'm firstborn American) so this was a huge sell for the Mac way back then

Sad to see that Windows is still stuck in the PS/2 days here

If you install Power Toys, you get a feature called "Quick Accent" which gives you a shortcut to get basically any symbol quickly. Hold down the key that's the most like the one you are looking for, and press space. A little menu pops up where you can cycle through all the variants.

So `- + space` brings up a menu with all the "dashy" characters. There's 12 of them!

There is also `Win + .` which brings up an emoji menu, where you can also access the symbols list.

The compose key works well on Linux. Typically mapped to right alt, compose-hyphen-hyphen-hyphen produces an em dash. (hyphen-hyphen-period produces an en dash.)

That's at least halfway between the difficulty of it on Mac and Windows.

Given the compose sequences are mnemonic, I’d prefer it over Mac every time. Compare Compose+<< and >> for «» to Opt+[ and Opt+Sh+[ on Mac. Which may or may not work depending on locale.

Not really. Maybe 20%.

Word and Outlook auto-replace double hyphens "--" with em-dashes "—", which is probably the most commonly used way on Windows.

Yeah, but that's not global. Mac has global keyboard entries for these things, and they are incredibly easy.