result.md

CustomManager.use_for_related_fields = False

Model	_base_manager	_default_manager
PlainModel	Manager	CustomManager
ModelWithAbstractParent	Manager	CustomManager
ProxyModel	Manager	CustomManager
MTIModel	Manager	Manager

CustomManager.use_for_related_fields = True

Model	_base_manager	_default_manager
PlainModel	CustomManager	CustomManager
ModelWithAbstractParent	CustomManager	CustomManager
ProxyModel	CustomManager	CustomManager
MTIModel	Manager	Manager

*.Meta.manager_inheritance_from_future = True

Model	_base_manager	_default_manager
PlainModel	Manager	CustomManager
ModelWithAbstractParent	Manager	CustomManager
ProxyModel	Manager	CustomManager
MTIModel	Manager	CustomManager

*.Meta.manager_inheritance_from_future = True
AbstractModel.Meta.base_manager_name = 'custom_manager'
PlainModel.Meta.base_manager_name = 'custom_manager'

Model	_base_manager	_default_manager
PlainModel	CustomManager	CustomManager
ModelWithAbstractParent	Manager	CustomManager
ProxyModel	Manager	CustomManager
MTIModel	Manager	CustomManager

test.py

def debug(model):
    print("{}\t{}\t{}".format(
        model.__name__,
        model._base_manager.__class__.__name__,
        model._default_manager.__class__.__name__,
    ))

    
class CustomManager(models.Manager):
  pass


class AbstractModel(models.Model):
    custom_manager = CustomManager()
    class Meta:
        abstract = True
debug(AbstractModel)


class PlainModel(models.Model):
    custom_manager = CustomManager()
debug(PlainModel)


class ModelWithAbstractParent(AbstractModel):
  pass
debug(ModelWithAbstractParent)


class ProxyModel(PlainModel):
    class Meta:
        proxy = True
debug(ProxyModel)


class MTIModel(PlainModel):
  pass
debug(MTIModel)