On Android you can install a custom launcher to get rid of that annoying Google Search bar, you can replace Google Search with DuckDuckGo's app, you can install Firefox for Android on it and completely replace Chrome, you can install apps from third party sources like F-Droid or Amazon's Appstore. In Marshmallow the previously broken permissions system has been finally redesigned. Chrome for Android is pretty cool lately, as it also does push notifications, the app manifest and it does a much better job for making web apps first class citizens than Safari on iOS or Firefox on Android or whatever Opera is doing. You can actually run Facebook in your Android browser now and pretend that it's a native app.
And Android is also open source, I mean yes, while it's dependent on Google's Play services, like for push notifications or its location services, those can be replaced and Android is very much fork-able. Hey, Amazon did it.
Ubuntu was doomed from the start and Android is light years away from its competition imho. I mean, experiments are cool, but if your mobile OS is less usable than Android from 5 years ago, that's a failed experiment.