sudo apt install screen
Open in edit mode the rc.local file:
sudo nano /etc/rc.local
Add the script that you want execute at startup. Remember to change SESSION_NAME with what your want and /home/test/myScript.sh with you script path.
screen -dmS SESSION_NAME bash -c '/home/test/myScript.sh; exec bash';
To check your script execution you can resume the screen session by executing the following command:
screen -r SESSION_NAME
Use the key sequence Ctrl-a + Ctrl-d to detach from the screen session.