class Section(models.Model):
  name = models.CharField(max_length=255, blank=False, null=True,)

class Product(models.Model):
  name = models.CharField(max_length=255, blank=False, null=True,)
  section = models.ForeignKey(Section,on_delete=models.CASCADE)

context['products'] = Product.objects.select_related('section').order_by('section')

{% regroup products by section as products_by_section %}

{% for section in products_by_section %}
    {{ section.grouper}}
    {% for product in section.list %}
        {{ product }}
    {% endfor %}
{% endfor %}