I’m also interested in the topic. I’ve never found the definitive answer to this question, and I feel that there is no one.
I’ve also read the “Django style guide for enterprise application.” Although there aren’t many things I could happily agree with, I love exploring how people do the business logic in Django and their approach was quite interesting.
I would happily listen to James’ opinion on service layers because I also don’t quite feel them and want to verify my thoughts.
As for business logic, I recommend reading this blog post: https://sunscrapers.com/blog/where-to-put-business-logic-django/. The author outlines the pros and cons of four popular approaches to doing business logic: Fat models, Views/Forms, Services, and Model managers.