That was almost certainly YouTube breaking itself. They do a lot of public A-B testing without notifying the user of anything, even if it could break functionality.

The chances of Librewolf breaking, and updating in 24 hours is basically zero. Especially if you're on Windows since it doesn't update itself, you have to choose to install the separate updater application when you install Librewolf, otherwise it just doesn't update.

https://codeberg.org/librewolf/librewolf-winupdater

https://librewolf.net/docs/faq/

How often do you update LibreWolf?

LibreWolf is always based on the latest version of Firefox. Updates usually come within three days from each upstream stable release, at times even the same day. Unless problems arise, we always try to release often and in a timely manner.

It should however be noted that LibreWolf does not have auto-update capabilities, and therefore it relies on package managers or users to apply them.

To be fair, YouTube is a giant piece of shit. On mobile, IronFox and Firefox are terrible with it, but switching to Chrome and everything loads instantly.

We all know Google is purposely slowing down non-chrome browsers.