How to make one account work only on one device?
As far as I know, it is not always possible to automatically receive a phone number.
And another nuance is that registration takes place on a third-party platform and the data already received there is used to enter the application.
Read device model and hardware data, save, check. Just like in desktop DRM, only in Android it is much more difficult to change some id or model in order to fit a new user – to bypass protection.