use com.adobe.granite.security.user.UserProperties instead. e.g.
UserProperties u = resourceResolver.adaptTo(UserProperties.class);
String email = u.getProperty(UserProperties.EMAIL);
This answer sends you down a frustrating dead end. I ended up using node logic to get through this. The com.adobe.granite.security.user.UserProperties library is not fully implemented and does not allow you to get the user properties. Instead, you are going to get null pointers when you try to build them. If I am wrong, please send me a fully implemented code usage with UserManager to Authorizable to UserProperties.
If I am not wrong UserManager is deprecated in 5.5.
Some thing like this you can try
String userId = adminSession.getUserID();
UserManager userManager = factory.createUserManager(adminSession);
Authorizable user = userManager.get(userId);
userName = user.getName();
That is deprecated code. The whole point was to stop using the deprecated code.