I see a privacy.firstparty.isolate, but no thirdparty variant. Was that just an error on your part, or is it a pref that needs to be manually created, even?
> Was that just an error on your part
Yes, sorry about that. It's privacy.firstparty.isolate
at least they made that really easy to find and do.
Follow the money.
It breaks things because a lot of websites expect it to work. If websites stop working then Mozilla will lose marketshare even faster. Still, it's not that difficult for people who know what they're doing to find.