I would not be surprised if the move to opt-out spying is consequences of the dropping ALSA and adding a hard dependency to pulseaudio fiasco.
Telemetry has been held as one of the main justification for the change as it supposedly showed only a fraction of users used ALSA. It turned out to be a combination of misinterpretation of collected data (installed libpulse does not mean not using ALSA) and a complete ignorance of the real world (most linux distros disable telemetry because privacy, people using ALSA are often the same that take extra measures to protect their privacy hence disabling mozilla spying mechanisms).
As a consequence mozilla pushed hard for package maintainers to enable telemetry in linux distros and sadly most did, see:
https://bugzilla.mozilla.org/show_bug.cgi?id=1233687
https://bugzilla.mozilla.org/show_bug.cgi?id=1285195
https://bugzilla.mozilla.org/show_bug.cgi?id=1285201
http://pkgs.fedoraproject.org/cgit/rpms/firefox.git/commit/?...
Compare to this from 7 years ago:
https://bugzilla.mozilla.org/show_bug.cgi?id=667577
The fun part was when mozilla people started patronizing users for protecting their privacy and told them that it's their fault if ALSA got dropped and that they should relinquish their privacy instead or they will be ignored:
Second, continuing to opt out of telemetry will just make problems
like this worse. As was stated in this thread, one of the
justifications for removing ALSA support was that the telemetry
numbers showed a very little ALSA usage. If more ALSA users had
telemetry enabled, perhaps the outcome would have been different.
In any case, running without telemetry means not having a say in
data-driven decisions about what configurations Mozilla should
support. It's OK to disable telemetry (that's why it's
user-controllable), but both users and distros that make decisions on
users' behalf should to take into account that if don't let Firefox
send info about your system config to Mozilla, your system config is
invisible to Mozilla's decision making about what to support.
source: Rationalising Linux audio backend support -
https://groups.google.com/forum/#!msg/mozilla.dev.platform/j...There was no course correction here, ALSA is still out despite the issue being entirely to mozilla implementation and not ALSA abilities, despite this being an edge case for linux netflix users with a specific 5.1 setup and despite someone coming forward to offer to fix and maintain their broken code.
Did I mention that they failed to mention this change in release notes, that firefox displayed a message inviting people to click a link to learn why their browser suddenly lost the ability to play sound but the link was broken and that this was an ESR release?
So when I read some mozilla marketing PR about them pretending to champion user privacy, I'm nonplussed at best.