I used to use UDL Helper, but for whatever reason it stopped working. I'm trying this one now, and so far it's working flawlessly.

Being able to choose from the various video sizes is also nice — sometimes I just don't need all that 1080 or 4K glory. But when I do, it's nice to have as well.

Hopefully this extension continues to work into the future, as I'm so tired of YouTube videos getting deleted and made into Lost Media unless someone downloads it.