Django M2M queryset with multiple instances and Q - django

Question

I have the following models:
class Thematics(models.Model):
title = models.CharField(max_length=255, null=True, blank=True)
def __str__(self):
return self.title
class Pathology(models.Model):
title = models.CharField(max_length=255, null=True, blank=True)
def __str__(self):
return self.title
class Organ(models.Model):
title = models.CharField(max_length=255, null=True, blank=True)
def __str__(self):
return self.title
class Surgerytype(models.Model):
title = models.CharField(max_length=255, null=True, blank=True)
def __str__(self):
return self.title
class Content(models.Model):
thematics = models.ManyToManyField(Thematics, null=True, blank=True)
pathology = models.ManyToManyField(Pathology, null=True, blank=True)
organs = models.ManyToManyField(Organ, null=True, blank=True)
surgery = models.ManyToManyField(Surgerytype, null=True, blank=True)
I have a lot of Content instances, which themselves have a lot of M2M instances related to them. You can think of Surgerytypes as tags.
I have this query:
content = Content.objects.all()
# surgeries is an array of Surgerytype instances titles
query = content.filter(Q(surgery__title__in=surgeries)
For simplicity I will focus on one M2M model, Surgerytype, and admit that I could replicate then chain the query with the 3 other models.
I create 3 instances of Surgerytype with title: "Diagnosis", "Surgery", "Therapeutic"
I then create 3 instances of Content to which I add these M2M relations with surgery (the M2M to Surgerytype)
Content instance 1 --> add(Diagnosis)
Content instance 2 --> add(Diagnosis, Surgery)
Content instance 3 --> add (Diagnosis, Surgery, Therapeutic)
The whole idea here is to have a dynamic filtering by the client/doctor who can choose tags to get to the type of content he needs.
So if he/she clicks :
on Diagnosis and no other tag, the doctor should see Content instance 1,2 and 3.
on Diagnosis and Surgery or just Surgery, the doctor should see Content instance 2 and 3
on Diagnosis, Surgery, Therapeutic or just Therapeutic, the doctor should see Content instance 3
On Diagnosis and Therapeutic, the doctor should see Content 3
So this is an AND problematic.
When I ajax send to my backend a tag (i.e. a Surgerytype instance title), all good the query returns all the instances of Content that include this tag. Now, the problem is that if I select two tags, the queryset returns nothing instead of all Content instances that include these 2 tags and possibly more tags. I have found on SO how to do this for 1 M2M model in the Content model but it is quite dirty and not scalable at all (there are 3 other M2M/filters to add in the real Content model). Any ideas? Found many questions related to the subject but it doesn't seem to have a definitive, scalable answer. Many thanks to you all