Within those rather fixed segments there is zero competition. (I said I limit my consideration to mobile operating systems, on phone hardware the situation is slightly different.) Zero competition is not market economy, so for me that means that Google's Android business must be regulated in an unprecedented way. Whether they gained their monopoly completely legally or not is just side topic. In practice that would probably mean that the Android business needs to be separated from the rest of the company and run as an utility or a non-profit until serious competition has developed again. I don't have the ready solution. The monopoly is unprecedented in history, so the solution needs to be so, too.
I am European, so the situation is even worse. Europe just waits and sees how US politics is busy with nearly losing democracy. A monopoly in the mobile operating system market is not very high on this agenda.
So what should Europe do? Create another Airbus? Introduce a heavy mobile operating system tax? I don't have good solutions, but just standing by is worse.