YouTube™ Comment Translate от BlanCow

Automatically translate YouTube comments on videos and shorts using the Google-Translate API.

This extension allows the user to translate YouTube comments with the click of a single button, right next to the comment.
This is useful, i.e. when listening to music from other countries.
The target language is customizable.
The sourcecode is openly available on GitHub.

The default target language is your browser language. To change it, click on the top right of firefox on the extension icon and select a new target language by clicking on the dropdown.

There's also a button to translate all visible comments.