In some cases one can install a de-googlified version of android, and install whatever app (.apk) they wish through alternative app stores or directly.
For 99.9% of people, Android and iOS will be virtually identical in terms of freedom, as they will just install apps from the play store and use google-services on the manufacturer-provided (and -bloated) android install that comes with their phone.
That being said, for those who do care, the ability to take control of your phone and run AOSP, an actually FOSS distribution, and only run FOSS apps, or install whatever app you want, is unparalleled on Android vs iOS.
