However, as an app ecosystem, it's not tough at all. For example, there is not a single open source email app on iOS which supports GPG email. In the iOS app ecosystem, privacy and FLOSS is an afterthought, since iOS users are more likely to pay for proprietary software. On Android, there are a lot more options, including things like F-Droid which are full of FLOSS apps which are graded based on their patterns and anti-patterns.
Even an open source app on these stores can't be provably correlated to published source code and could have undocumented deviations at any time.
Put simply, there is no reasonably accountable privacy story on stock iOS or Android. You mostly just have to take each publishers biased word for it and that the permissions systems alone covers every potential way an app can abuse your trust.
And it doesn’t seem tough to generally diff privacy between the two OSes, as this paper seems to add some contributions.
But I agree andriod being in hands ads company has really no incentive to be privacy friendly. Apple mostly selling hard generally have incentive to be more privacy friendly.