Android is going to be adding developer ID verification for any developer that wants their app to be sideloaded onto more than 20 devices.

You might be wondering: how are they going to track that? Well it turns out they already have been. Google Play Protect is sending the hashes of the apps you install back to Google's servers.

Your unique device identifier, your account info, and the apps you run are stored on Google's servers, even for a local install of a sideloaded app.