After showing the "Select default app" dialog for the user for the second time on Android 10, it will add the additional option "Don't ask again". If the user chooses it and hit the "Set as default" button on an app that is not yours, then next time, you will not be able to show this dialog to the user. An immediate result of denial will return.
How to detect when the user is hitting the "Don't ask again" option?
Note that this is different from hitting the never ask again option on the permissions dialog.