Macs and iDevices have been auto-transforming -- into – for well over a decade now, and on the iOS standard keyboard both – and — are just a single long press of the dash key away.
Still less obvious than the emails I see sent out which contain emojis, so maybe I'm overthinking things...
Also you can ctrl-z immediately after an autocorrect to undo it.
In certain places it does seem to do the substitution - Notes for example - but in comment boxes on here and (old) Reddit at least it doesn't.