If you use GeoDjango your models require a GeoManager model manager. If you use django-polymorphic for inheritance in Django your models require a PolymorphicManager model manager. What if you need both functionalities? Then use this manager: GeoPolymorphicManager

geoPolymorphicManager.py

from django.contrib.gis.db import models
from django.contrib.gis.db.models.query import GeoQuerySet
from polymorphic import PolymorphicManager
from polymorphic.query import PolymorphicQuerySet


class GeoPolymorphicQuerySet(GeoQuerySet, PolymorphicQuerySet):
    '''
    QuerySet used in GeoPolymorphicManager.
    '''
    pass


class GeoPolymorphicManager(models.GeoManager, PolymorphicManager):
    '''
    GeoManager with polymorfism functionalities (for django-polymorphic).
    '''
    queryset_class = GeoPolymorphicQuerySet

    def get_query_set(self):
        return self.queryset_class(self.model, using=self._db)

Simple and effective.

Good morning, fellow googlers.

The above solution doesn't work (any more). I've modified it slightly, and also added a base model, for simplicity.

from django.contrib.gis.db.models.query import GeoQuerySet
from polymorphic.managers import PolymorphicManager
from polymorphic.models import PolymorphicModel
from polymorphic.query import PolymorphicQuerySet


class GeoPolymorphicQuerySet(GeoQuerySet, PolymorphicQuerySet):
    pass


class GeoPolymorphicManager(models.GeoManager, PolymorphicManager):
    """
    GeoManager with polymorphism functionalities (for django-polymorphic).
    """
    queryset_class = GeoPolymorphicQuerySet

    def get_query_set(self):
        return self.queryset_class(self.model, using=self._db)


class Model(PolymorphicModel):
    objects = GeoPolymorphicManager()

    class Meta:
        abstract = True

This does not work anymore:

$ pip freeze | grep -i django
Django==2.1.3
django-bootstrap3==11.0.0
django-debug-toolbar==1.10.1
django-geojson==2.11.0
django-leaflet==0.24.0
django-polymorphic==2.0.3

$ python -c 'from django.contrib.gis.db.models.query import GeoQuerySet'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'django.contrib.gis.db.models.query'