On mobile it's long-press the hyphen on the keyboard.
On Windows I use https://cemrajc.github.io/em-n-en/ so that ==- is turned into it system-wide.
On recent Ubuntu versions, you can set up Compose Key, for example with Caps Lock: https://www.danielkossmann.com/how-to-get-em-dash-ubuntu-lin...
I've long been an em-dash user and enjoyer and hope that using it stops becoming such a signal for AI text.