Is there any way to change username field label in user authentication login page?

According to documentation LoginView has an attribute called authentication_form (typically just a form class). Defaults to AuthenticationForm.

You can create a form class that inherits from AuthenticationForm, set the label of the username field and assign it to your LoginView over authentication_form attribute.

forms.py

from django import forms    
from django.contrib.auth.forms import AuthenticationForm, UsernameField


class CustomAuthenticationForm(AuthenticationForm):
    username = UsernameField(
        label='Team Name',
        widget=forms.TextInput(attrs={'autofocus': True})
    )

views.py

from django.contrib.auth.views import LoginView

from .forms import CustomAuthenticationForm


class CustomLoginView(LoginView):
    authentication_form = CustomAuthenticationForm

urls.py

urlpatterns = [
    path('login/', CustomLoginView.as_view(), name='login'),
]

Just change the label's text of your username field like this:

 class LoginForm(ModelForm):
    class Meta:
        model = YourModel
        fields = ['username','password']

    def __init__(self, *args, **kwargs):
        super(LoginForm, self).__init__(*args, **kwargs)

        for fieldname in ['username']:
            self.fields[fieldname].label = 'Email'

All you have to do is override the Django admin authentication form. In my case, I needed to override the username label since I wanted to allow users to use either their phone number or email to log in.

forms.py

 from django import forms
 from django.contrib.admin.forms import AdminAuthenticationForm
 from django.contrib.auth.forms import AuthenticationForm, UsernameField
 from django.utils.translation import gettext_lazy as _


class CustomAdminAuthenticationForm(AdminAuthenticationForm):
    """
    A custom authentication form used in the admin app.
    """
    error_messages = {
        **AuthenticationForm.error_messages,
        'invalid_login': _(
            "Please enter the correct phone number or email and password for a staff "
            "account. Note that both fields may be case-sensitive."
        ),
    }

    username = UsernameField(
        label='Email/Phone number',
        widget=forms.TextInput(attrs={'autofocus': True})
    )

admin.py

import CustomAdminAuthenticationForm from {whatever_location}

from django.contrib import admin

admin.site.login_form = CustomAdminAuthenticationForm