On Wed, 15 Dec 2021, Lynx Medeiros wrote:
Yes, the problem is with Firefox, there is no sound when viewing Youtube.
This may not be of any help, but I remember reading a thread in a usenet ng (Ubuntu?) that resulted in the finding that Firefox required a sound library file only provided in the distro non-free selections. Whereas the "other" browsers had the ability built in. It may have been an issue with a 'flavor' of mp4, IDK.
It was not an issue I had much interest in.
I can't help any further, and the above comes from a frail and fragile memory. :-)
Good Luck!