I don’t understand how they are supposed to “sell your data” if you just never use a Mozilla account and uncheck all the telemetry. Its not like they can secretly steal your data, since its Open Source.
It seems to me like just more FUD that Google is spreading to undermine our trust in free software.
This is mitigated by “reproducible builds”
Does Firefox do reproducible builds? This bug report makes me think it doesn’t (at least for Linux): https://bugzilla.mozilla.org/show_bug.cgi?id=885777
But maybe they do for Windows/Apple/Android?
Not sure. But you can change that, if not