I'm pretty sure browser share is done by useragent, which will report Firefox if you're using Firefox. Unless of course you change your useragent but the number of people doing that will be vanishingly small.
To be fair, one of the very few add-ons available for Firefox on Android is an add-on that does exactly this on Google properties so Google won't degrade your experience for using FireFox.
So maybe it is more popular than we think. Very hard to know for sure.
Not sure you can really blame android, when Android allows Firefox as a first class replacement for Chrome and with ease for the user, whereas iOS doesn't even allow the real Firefox.
iOS is a very important platform for Firefox, so apples anti-competitive behavior in this regard really undermines firefox's future.
I'm very sad that this issue has not come up in all of the debate about the app store.
~98% of Androids use the default browser, which is an incredible amount of people, like in the billions. We tend to forget iOS is a minority worldwide.
Not sure it's reasonable to ask a for-profit company to do more than make it easily and fully changeable. Neither Microsoft nor Apple come close to that.
Dark patterns from Microsoft and Google. They nag users to set their own applications as the default. You can't expect users who don't know any better to to always say no, they get tired and then say yes.
Because the reasons why its market share ever got as high as it did to begin with no longer apply. Firefox isn't basically competing with a piece of abandonware that happens to ship with Windows any more.
