[Django]-Django – combining two models serializer into one JSON response

You can also use SerializerMethodeField https://www.django-rest-framework.org/api-guide/fields/#serializermethodfield.

class ListSerializer(serializers.ModelSerializer):
    cards = serializers.SerializerMethodField()

    class Meta:
       model = List
       fields = '__all__'

   def get_cards(self, obj):
       data = CardSerializer(obj.card.all(), many=True).data
       return data

change the list related_name to cards and ListViewSet will do what you want

class Card(models.Model): # to create card table
    title = models.CharField(max_length=100)
    description = models.TextField(blank=True) 
    list = models.ForeignKey(List, related_name = "cards"
    ,on_delete=models.PROTECT)
...