Having read through the article, I still don’t know how to spot a toxic boss at the interview stage.

This seems like a good guide for corperate jobs, but as someone who has worked in retail and food service for most of their life, a good indicator is to go to the place first as a customer. Watch the employees, see if they’re smiling or if they look upset. If someone is looking haggard and miserable on a slow Wednesday afternoon you know it’s a shit job. Also the turnover suggestion is a good thing that I think applies to all jobs