ManyToMany with through: ForeignKey not showing in admin

I have a ManyToManyField using through:

class Entity(models.Model):
    relationships = models.ManyToManyField('self', through='ThroughRelationship', blank=True)
        
class ThroughRelationship(models.Model):
    entity = models.ForeignKey(Entity, on_delete=models.CASCADE)
    name = models.CharField()

I'm adding it to admin like this:

class ThroughRelationshipInline(admin.TabularInline):
    model = ThroughRelationship
    extra = 3

@admin.register(Entity)
class EntityAdmin(admin.ModelAdmin):
    inlines = [ThroughRelationshipInline]

However, in the admin panel, only the name field is showing, I can't select an entity. How can I fix this?

The ThroughRelationShip does not make much sense. Even if you have a ManyToManyField to the same model, it should imply two ForeignKeys, since the ThroughRelationShip is essentially a "junction table" that links two entities together, so:

class Entity(models.Model):
    relationships = models.ManyToManyField('self', through='ThroughRelationship', blank=True)
        
class ThroughRelationship(models.Model):
    entity_from = models.ForeignKey(Entity, on_delete=models.CASCADE, related_name='relations_by_from')
    entity_to = models.ForeignKey(Entity, on_delete=models.CASCADE, related_name='relations_by_to')
    name = models.CharField()

and then work with:

class ThroughRelationshipInline(admin.TabularInline):
    model = ThroughRelationship
    extra = 3
    fk_name = 'entity_from'

@admin.register(Entity)
class EntityAdmin(admin.ModelAdmin):
    inlines = [ThroughRelationshipInline]
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