Some tips like post it notes, various alarms to remind him. My D20 uses her smartphone for reminders- to schedule doing and turning in work. An executive function coach, even informal/free- to come up with calendar time management strategies is helpful.
Getting a part-time job helped my D20, though he may need to wait til spring or even summer once grades are back on track.
See resources like “Late, Lost, Unprepared” by Dr Joyce Cooper Kahn
https://www.additudemag.com/late-lost-and-unprepared/