I find I can’t push myself to finish things until there is a hard deadline, no matter how much I tell myself I will do things earlier. My last subject let you submit your assignments up to one week after to due date with no penalty, so I didn’t do any of the assignments until the last day of that week after the due date.

ADHD might make it harder to organise yourself to get things done, but I don’t think flexible deadlines are a good answer - especially as there is always a hard deadline for the end of the subject that can’t be flexible, and you run the risk of everything piling up at the end. Plus it stops you getting feedback on earlier assignments in time for them to be useful for the next one.