So, the answer for my question was actualy unaccent
lookup since I am using PostgreSQL.
Here are the docs: https://docs.djangoproject.com/en/2.2/ref/contrib/postgres/lookups/#unaccent
This lookup field does not work right off the bat, first one needs to install unaccent extension.
Credits to this answer - easy way to do that is to create empty migration and add unaccent extension with Django.
python manage.py makemigrations --empty <app_name>
Then in the new migration file:
from django.db import migrations
from django.contrib.postgres.operations import UnaccentExtension
class Migration(migrations.Migration):
dependencies = [
('app_name', '<parent_migration>'),
]
operations = [
UnaccentExtension(),
]
Now I can do desired query like this:
City.objects.filter(name__unaccent__iexact='koln')
And it works just as expected :)