If you wrote the type signature of get_user as tuple[User, None] | tuple[None, Exception], the assertion would not be necessary and the type checker wouldn’t complain.

and even today, by using an old Android API iirc

Nope, the required API to have your app in the Playstore constantly rises, and if you don’t comply you get kicked. The current API version is something around 26, and definitely has the permissions model integrated.

Well how do you want to use said get function?

let x = config.get("key").await;

So what type should x have?