Using python I got a script to trigger the proper keystrokes to get LightBurn to fire the laser on the rubberband frame operation!
apt install python3-pip python3-tk python3-dev
pip install pyautogui
import pyautogui
# this did not work
#pyautogui.hotkey('shift','alt','r')
# this works
pyautogui.keyDown('shift')
pyautogui.keyDown('alt')
pyautogui.keyDown('r')
pyautogui.keyUp('r')
pyautogui.keyUp('alt')
pyautogui.keyUp('shift')