Adding a link with the thumbnail, originally used by YouTube is a solution, that works. The thumbnail, used by YouTube is accessible the following way:
https://www.youtube.com/watch?v=5yLzZikS15k
https://img.youtube.com/vi/5yLzZikS15k/0.jpg
Following this logic, the code below produces flawless results:
<div align="left">
<a href="https://www.youtube.com/watch?v=5yLzZikS15k">
<img src="https://img.youtube.com/vi/5yLzZikS15k/0.jpg" style="width:100%;">
</a>
</div>
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