Use the GPG pinentry-mac app for SSH keys

ssh-pinentry.sh

#!/bin/sh
#
# chmod +x this script and set it as SSH_ASKPASS.

set -euo pipefail

urldecode() {
  python -c 'import sys, urllib; sys.stdout.write(urllib.unquote(sys.stdin.read()))'
}

pinentry-mac <<EOM | grep '^D ' | sed -e 's/^D //g' | tr -d '\n' | urldecode
SETDESC ${1:-Please enter the passphrase for your SSH key}
GETPIN
EOM