Custom User model fields (AbstractUser) not showing in django admin

You have to override UserAdmin as well, if you want to see your custom fields. There is an example here in the documentation.

You have to create the form for creating (and also changing) user data and override UserAdmin. Form for creating user would be:

class UserCreationForm(forms.ModelForm):
    password1 = forms.CharField(label='Password', widget=forms.PasswordInput)
    password2 = forms.CharField(label='Password confirmation', widget=forms.PasswordInput)

    class Meta:
        model = User
        fields = '__all__'

    def clean_password2(self):
        password1 = self.cleaned_data.get("password1")
        password2 = self.cleaned_data.get("password2")
        if password1 and password2 and password1 != password2:
            raise forms.ValidationError("Passwords don't match")
        return password2

    def save(self, commit=True):
        user = super().save(commit=False)
        user.set_password(self.cleaned_data["password1"])
        if commit:
            user.save()
        return user

You override UserAdmin with:

from django.contrib.auth.admin import UserAdmin as BaseUserAdmin

class UserAdmin(BaseUserAdmin):
    add_form = UserCreationForm
    add_fieldsets = (
        (None, {
            'classes': ('wide',),
            'fields': ('email', 'first_name', 'last_name', 'is_bot_flag', 'password1', 'password2')}
        ),
    )

and then you register:

admin.site.register(User, UserAdmin)

I pretty much copy/pasted this from documentation and deleted some code to make it shorter. Go to the documentation to see the full example, including example code for changing user data.

If all you want to do is add new fields to the standard edit form (not creation), there's a simpler solution than the one presented above.

from django.contrib import admin
from django.contrib.auth.admin import UserAdmin

from .models import User


class CustomUserAdmin(UserAdmin):
    fieldsets = (
        *UserAdmin.fieldsets,  # original form fieldsets, expanded
        (                      # new fieldset added on to the bottom
            'Custom Field Heading',  # group heading of your choice; set to None for a blank space instead of a header
            {
                'fields': (
                    'is_bot_flag',
                ),
            },
        ),
    )


admin.site.register(User, CustomUserAdmin)

This takes the base fieldsets, expands them, and adds the new one to the bottom of the form. You can also use the new CustomUserAdmin class to alter other properties of the model admin, like list_display, list_filter, or filter_horizontal. The same expand-append method applies.