Is it possible to login with different username?

                    <form title="msg://loginForm.headerTitle"
                          username="msg://loginForm.username"
                          password="msg://loginForm.password"
                          forgotPassword="msg://loginForm.forgotPassword"
                          submit="msg://loginForm.submit" />
                    <errorMessage title="msg://loginForm.errorTitle"
                                  message="msg://loginForm.badCredentials"
                                  username="msg://loginForm.errorUsername"
                                  password="msg://loginForm.errorPassword"/>
                </loginForm>

For example, user login want to login with username or email.

Hi,

There is no such out-of-the-box functionality. User has single username.

As a possible custom solution (for a standard Jmix authentication):
Create an entity that represents mapping between some “virtual” usernames and a “real” username.
You will need some configuration UI to fill it (can be part of User view).
Then use it in your Login view - resolve “real” username by input value and use it for further authentication.

Also you will have to maintain uniqueness among “virtual” and “real” usernames (if there is a “real” username A then there can’t be “virtual” username A mapped to someone else).

Regards,
Ivan