In the mobile industry, there are two that conquer almost everything.
They are competitors, differentiating themselves by only their names and products They come and steal the market; by robbing it, copying others, or just by buying competitors to eliminate the competition.
They are Google and Apple. So yes, two can play this game.
The duopoly giants that occupy most of the market, has the power to revoke or grant anything they wish. Mostly because in the modern age of the internet, the majority comes from mobile, a field where Google with Android and Apple with iOS have secured a safe position.
And because a growing majority of all web traffic also comes from mobile devices, they too control the freedom of speech on the internet. Unless policymakers can act to create a law to limit their corporate grip.
Any apps that follow their guidelines, can be included in their respective mobile app store. But if they dislike an app for any reason, the app won't be included in the app store, significantly reducing their reach.
For Android users, they can still grab unapproved apps from Google's Play store by enabling the option in the phone's setting. But this can be a cumbersome process and less safe for users.
As for iOS users, this is a different story. iPhone and iPad users can't use apps that Apple disapproves.
At a minimum, Apple and Google’s decisions about app behavior are mostly based on random choice or personal whim, rather than any reason, guidelines or system.
This is a something that the market can't easily solve. The reason is simple: because Google and Apple are the market. Since both Google and Apple's app stores are private markets owned by those companies, the two companies are essentially governing it.
No company can start a mobile business with ease without their permission.
Regardless anyone's view, neither Google or Apple should govern the mobile internet. They shouldn't be the corporate gatekeeper of free speech because it may limit healthy competition, or even eliminate them altogether.