Beginning very soon, you'll need to have the JavaScript runtime Deno installed to keep YouTube downloads working as normal.
Why?
Up until now, yt-dlp has been able to use its built-in JavaScript "interpreter" to solve the JavaScript challenges that are required for YouTube downloads. But due to recent changes on YouTube's end, the built-in JS interpreter will soon be insufficient for this purpose. The changes are so drastic that yt-dlp will need to leverage a proper JavaScript runtime in order to solve the JS challenges.
What do I need to do?
Everyone will need to install Deno.
yt-dlp will also need a few JavaScript components, and this may require additional action from you depending on how you installed yt-dlp: