On MacOS: Opt+Shift+-

En dash is the same without the shift

There were a couple years where spelling/ grammar checks where it would always correct like half of the regular dashes id use into em dashes, and id have to copy an email dash after I spell checked, then ctrl +f all the regular dashes and replace them with the coppied em dash

just do like I do, go to wikipedia and copy the character from the page for it.

but on the internet, you might also be able to do —, depending on if it's allowed.