I searched and searched for the solution within the community to find an answer to this "simple" problem. This message is to provide the solution to you if you are looking for the same thing - You want to add a mp4 video not a YouTube video to the home page of your theme.
Here is the solution: https://www.youtube.com/watch?v=FcB580SjU_Q
Here is the file link: https://itfam.pro/video-background-shopify-debut-theme/
After downloading and unzipping the file, change its name to: video_background.liquid.text and open it with notepad. You can then copy and paste it as directed in the video.
I hope this helps someone looking to add a mp4 (not a YouTube video) to their home page.
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