714
Open Letter to Tim Cook: Sabotaging Web Apps Is Indefensible
(letter.open-web-advocacy.org)
A place to discuss the news and latest developments on the open-source browser Firefox
Not tried in a while but it used to just be a case of leaving it disconnected from the net during setup.
Failing that you can still sign up with a throwaway account and convert it to local in the options after installation iirc. It's not ideal but it's still something at least.
There are additional steps now which I mentioned.