Remapping keys without karabiner

change-rightalt.sh

hidutil property --set '{"UserKeyMapping":[{"HIDKeyboardModifierMappingSrc":0x7000000E6,"HIDKeyboardModifierMappingDst":0x700000068}]}'

kr.hakk.RAltF13.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<!-- Place in ~/Library/LaunchAgents/ -->
<!-- launchctl load kr.hakk.RAltF13.plist -->
<plist version="1.0">
  <dict>
    <key>Label</key>
    <string>kr.hakk.RAltF13</string>
    <key>ProgramArguments</key>
    <array>
      <string>/usr/bin/hidutil</string>
      <string>property</string>
      <string>--set</string>
      <string>{"UserKeyMapping":[{"HIDKeyboardModifierMappingSrc":0x7000000E6,"HIDKeyboardModifierMappingDst":0x700000068}]}</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
  </dict>
</plist>

Persisting across reboot: https://stackoverflow.com/a/46460200