I switched to a fork of Firefox (Zen) without their bs..

Now imagine if they had something to advertise which people actually want!

So long as they remain open source

I don't see how they think it's a good move. I'm not speaking about people being upset. Most of the Firefox users are either people having at least some tech knowledge or people which use it because of a person with some tech knowledge.

And most of these people use an ad-blocker, know how to install a fork and so on. So, from the beginning, I don't know who think it's a good idea other than to kill Firefox.

Well, Thunderbird gives me hope.

How it's been going.

https://www.youtube.com/watch?v=-QbBc3Oduc8