You can type it in Terminal with Opt-E, a. If the iOS “hold a and select choice” method worked, you’d lose key auto repeat, making things like hjkl navigation in vi fail. There’s a [command to flip the behavior](https://www.howtogeek.com/267463/how-to-enable-key-repeating-in-macos/), but I believe the default is correct for Terminal. I’ve found [a variation of that command](https://stackoverflow.com/a/44010683/142454) useful for allowing repeat-on-hold for use with the Vim extension for VSCode, though. This Alt-hex code stuff sounds like Linux, not macOS.