It might help to remember the Rule Of Three when it comes to ADHd.
The adolescent ADHD brain,(some would say adult brains as well!), is functioning about 1/3 younger than its chronological age in terms of “maturity”. A 17 year old, no matter how brilliant, is really a 12-13 year old in disguise! Few 13 year olds would feel ready to fly the coop, some are downright terrified at the prospect, and rightly so. “Launching” timelines are highly arbitrary and individual. When your son feels ready, there’ll be no holding him back. It just might not happen for a few years yet.
Meanwhile, enjoy having a kid around who actually wants to be with you. You’ll miss that when it’s gone, promise. “Extended” adolescence can be a gift of time most parents don’t get.