I have implemented firebase auth (through Google) on Flutter, but I cannot seem to be able to retrieve more user data other than email, picture and name.
I'm interested in age and sex of users. Also, I don't know why but also on the firebase dashboard those data don't seem to be retrieved after login.
Unfortunately Firebase doesn't provide these information, for retrieving that, you can use the ID that you retrieved after the login with external services.
E.g. for gender you can use https://developers.google.com/people/ API.
Flutter seems like a package that is developed by Google Engineers, for Google APIs including people, you can use it. (I haven't done this operation on Flutter, I know it from Android.)
If you are familiar with Android you can check this question and answers.
