Community college is a great place to start, allows you to get your toes wet without too high stakes. Speaking as a software engineer, don't worry to much about the adhd stuff, there are a lot of us in the tech field (being able multi-task well and hyperfocus on something we are somewhat interested in are actually pretty valuable in his field). I'd probably advocate for making sure you adhere to a strict schedule for a bit when first starting out, makes it easier to not burnout on school long term (it's hard I know, but once you establish those little habits school stays more managable).