t probably didn’t have anything to do with Firefox itself

It probably did. Google has been caught red-handed with messing with Youtube to break Firefox.

https://www.reddit.com/r/youtube/comments/17z8hsz/youtube_has_started_to_artificially_slow_down/

And is there any way to play songs by folder with rhythmbox yet? Haven’t looked into it for a while.

I really really don’t get why you just can’t organize your music in plain old folders with rhythmbox. Not Playlists, not Meta data. Just folders. Ist it that exotic? Is it that hard to implement?