Quote
Zvonko
Who or what changes such a setting--or another setting--somewhere in the background and causes such problems?
Nobody, nothing.
As mentioned by Rodocop and as you could see on your own installs, the
default value is
true.
Quote
Zvonko
And: On my other computer the value is set to true, an there are no Yotube problems...
As you have noticed the default value works with YT on your other computer.
So it works for most people (btw, for me too).
The reason it doesn't work on all computers might be hardware related.
BTW, in more recent Firefox ESR the above pref was removed being replaced by other prefs.
Quote
siria
For media playback Mozilla has created so countless prefs and settings, and combinations with yet other prefs, it's just a jungle now. And of course sites like youtube also contribute to the mess, continuously changing their own requirements. Gruesome.
Blame YouTube/Google.
Browser vendors have no other choice but to make their browser working with YouTube (as with other services owned by Google as well) and follow the guidelines enforced by Google.