sideloading is possible too ( not on iOS ) but idk if you want to go down that road (one example being putting games up on epic store “partially”. Fortnite is installed from epic’s site right now afaik ). I assume discoverability of app is of interest too, not just the means to download/pay
If that’s about Google play account block situation, it has other issues. All CI games worked with AD before, people watch AD to continue playing while developer gets revenue, and if he said he’ll have to stop active CIU development until the situation gets solved, I assume revenue was big enough. Google Play market is the most used app store for the most of mobile devices, and AD works via Google, too.