Quiet Feed by Navjot Suman

Quiet Feed hides distracting elements on video feeds — short-form clips, home page recommendations, the related-videos sidebar, comments, and end-screen suggestions — each toggled independently from the popup.

Runs 100% locally: no accounts, no servers, no analytics, and no network requests of any kind. The source is plain, unminified JavaScript and CSS you can read in full. Settings are stored only in Firefox's built-in storage.sync, which syncs across your own signed-in devices and is never sent anywhere else.