Custom joins for django. Probably works with 1.11 and 2.x.

custom_django_join.py

class CustomFromSQL(object):
    def __init__(self, sql):
        self.sql = sql

    def as_sql(self, compiler, connection):
        return self.sql, []

    def add_to_queryset(self, queryset):
        alias = hash(self.sql)
        # Django iterates over query.tables
        queryset.query.tables.append(alias)
        # checking that query has references to this table
        queryset.query.alias_refcount[alias] = 1
        # and take froms and joins from query.alias_map
        queryset.query.alias_map[alias] = self


def test_custom_join():
    qs = User.objects.filter(age__gt=18)
    custom_join = CustomFromSQL('JOIN user AS user2 ON user2.gender <> user.gender AND user2.age == user.age')
    custom_join.add_to_queryset(qs)
    return qs