If you don’t want YouTube to suggest and show related videos at the end of your embedded video, we can add this parameter rel=0 at the end of the URL.
<iframe width="720" height="405" src="https://www.youtube.com/embed/o1sML93K5M4?si=ls-lKs7yCb3rHsJM&rel=0"
title="YouTube video player"
allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share"
referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
That’s it! See the demo.
I got the idea from reading this post.