The issue of non-ASCII-constrained environments is that it's still not easily accessible on most keyboards.
I do know and use the compose key but it's not the same as having a standard key for it. Trying on a mobile device, long pressing the dash key there suggests 2 dashes (not sure if the second choice is en-dash or em-dash), which is some but that's not the 4 types discussed here.
Do you know one where it's easy to type? There are many international keyboards but I don't think any has that many dashes. Compose key is the best I think.
I do know and use the compose key but it's not the same as having a standard key for it. Trying on a mobile device, long pressing the dash key there suggests 2 dashes (not sure if the second choice is en-dash or em-dash), which is some but that's not the 4 types discussed here.