VPN, FPN (https://fpn.firefox.com/) or Pocket Premium. All of those go to the corporation directly, not the foundation.
Out of the three, only Pocket is widely available. FPN is US-only, VPN is only available in like 5-6 countries.
I don't think their revenue per user has really changes, their problem has been the regular drop in usership. Your money can't offset millions fewer users, which is why they aren't screaming for donations.
Organize a non-fork alternate development team, accept crowdfunding for specific goals/features.
Yes. Or Pocket Premium.
Donations will increase Mitchell Baker compensation even further, and won't help the browser. I think at this moment donation will corrupt Mozilla even further. Better keep money until they fix the management.
That supports mozilla foundation, which uses the funds for advocacy, but it doesn't support the development of firefox, which is done by the mozilla corporation.