You have a point about iPhones, though. It's almost pointless, but not quite: it does get a few features, like cross-platform sync. "Real" Firefox is one of the things that keeps me on Android.
1) Apple would never force "Chromium" on any of their platforms. You might be mistaking it for WebKit, but browsers are not required to use Apple's shipping version of WebKit on a Mac either.
2) Firefox on every single platform not on the iPhone & iPad uses and has always used Gecko. I'm not aware of any other exceptions besides those two platforms, but the Mac definitely isn't one of them.
1. These can all be disabled by advanced users (largely without consequence)
2. They dont prevent things like installing apps or even gaining root access in the first place.
The very fact that you can install Linux is evidence of the different approach taken with macs (you can't easily install Linux of ios devices)
I have always been able to.
Most of them also work with Linux, although it's a little more spotty on the more recent ARM-based ones ("apple silicon").
Macs are essentially "real computers" that you can run whatever software you want on, whereas iPhones and iPads are much more locked down. (Even when they have the same CPU.)
After a month or so, I gave up and switched back to FF.
I'm on a mac and happily use Firefox. Have done for over a decade. It would take a lot to encourage me to move to a proprietary browser (Edge, Chrome, Safari).
Maybe I'm out of touch, but the attachment to Chrome that some people seem to have (despite the outright privacy abuse) is baffling to me. I mean, ffs, are a couple of minor UI compromises (not that I experience any - quite the opposite) enough to justify what I consider a frankly perverted browser experience? I'm inclined to conclude that some people have little self respect - being so willing to metaphorically undress for the big G's benefit.