> On Mac at least, I'm not aware of any viable non-Chromium alternatives

Surely Mac is the only place there is a viable non-Chromium alternative (Safari)?

There are a ton of Firefox forks, especially in order to keep Firefox but without these sort of shenanigans.

The only problem is: what's the difference between the forks, and which is the best? I have no idea.

I use the Duck Duck Go browser for almost everything. I is open source for iOS/Android/macOS platforms, but I think there are parts of their platform that are not. The DDG browser hits all my privacy requirements.

What problems do people have? I use Firefox on Mac since a decade at least.

Orion is pretty viable alternative. Based on WebKit.

I prefer Firefox over Chromium. But I much more prefer having a working ad blocker. Therefore I support that statement and when Firefox starts removing support for that, I'm out and there's enough alternatives I can go to, even tho they're Chromium based.

Zen is basically Firefox with Arc's UX. It's by far my favorite browser.

...Safari??

Apple doesn't collect your browsing data, they build in privacy controls that are pretty much as strong as they can manage given the state of the world, and while it doesn't support uBO, it supports a variety of pretty solid adblockers (I use AdGuard, which, AFAICT, Just Works™ and even blocks YouTube ads most of the time, despite their arms race).

Use Brave the privacy is better than Firefox already.