I just started using this extension a few minutes ago.
After many years of searching, it seems I finally found one that actually works like I want.
Sweet!

Nice, but prevents Video Speed Controller from working even when its not on but just actively installed.

Brakes youtube speed options.

I would prefer at least 15 slicers over FQ but otherwise seems quite good.

最高です！！
Android版Firefoxでも使えます。
PC・Android共に愛用しています。

No perceptible difference in audio volume no matter what you do

Although the mono feature I got this for works, it breaks the HTML5 speed controls such as built into YouTube or from the Global Speed extension.

No perceptible effect. Ubuntu Fossa Firefox 76.9 Canonical 1.0

Quite good. not the best