By default rails g activeadmin_settings:install add mount_activeadmin_settings() route at the top of route.rb i.e. before active_admin routes that would already be there.
Although, this doesn't cause major issue it does cause problem with user route overriding /admin/user route. So Users link in top nav doesn't point to list of users but points to list of admin users.
Ideally, rake task should be updated to add route at the end of routes.rb or this issue should be mentioned in Readme.