TuanPhan, I am having the same problem. I am having to use the CSS code to prevent unwanted videos being displayed on my website from YT "suggested" videos options. I have also tried adding your code but it does not work? PS I am NOT a coder, nor do I have any experience in writing CSS. I am including a screen shot of a CSS block within my SQSP site, with the CSS window opened up. I'll also provide a link to this exact page below. Could you type in EXACTLY where your code should be put into my CSS block?
https://www.bbcfunding.com/real-estate-investors/5ws-of-private-lending