The board's software coding doesn't like the newer http links (the ones with the youtu.be designation). I usually just paste that one into the address bar to go visit it and then copy the resulting longer address to use on Halloween Forum.
So using your example:
I'd go to https://youtu.be/RLJ_9id2yik, and once on that page, I'd see the following actual address in the web browser:
Copy THAT address and paste it into the