Three years ago, I was in your shoes. DS had no idea what he would want to study at university, so he left (with three A levels, nothing spectacular). He always liked cooking so we sent him on a crash cookery course, thinking that he might do a chalet season. At the end of it, he dropped his CV in at a few places and was offered a junior chef job at a very smart small hotel, with a big food reputation, and he stayed for most of the next two years.
Last winter, his maths teacher (who's his BF's mum) said to him "XingJr. it's time to consider university again". He did, he applied and started in September, and has just finished his first semester with a First on one module, and only 3 marks adrift from a First on two others. He's loving the course, and completely committed.
So you may just need to be patient, and insist that he gets a job, any job. For my DS, it was understanding that work is different to school and that you stand or fall on your own efforts but that being reliable and toughing it out is essential. But a professional kitchen is hard graft. DS went from school to working 70 hours a week on MW. He grew up very very fast in 18 months. All that said, hospitality is closed now, so there are not many openings anywhere.