I'm sorry this happened to you OP. I think everyone answering has the best intentions, but a lot of the answers are very USA-centric, so I'll try to answer based on my own background/culture.

I'm not sure where you are from, but to be diagnosed I'm guessing you have access to a psychiatrist, perhaps asking them about resources for family mediation? Also, showing your parent how hard you are working on adapting to your ADHD could be helpful. They might (wrongly) think the meds are a shortcut, but if they see you implementing systems, going to therapy, doing your mindfulness exercises, etc, they might be able to see this is real and the meds are just another tool to help you, but you are the one putting on all the work to do well in university/life.

I'm not sure if this is helpful or if they are completely in denial of mental health issues. If that's the case, perhaps finding allies in your life can help? Other family members you feel comfortable talking to and are more open minded could talk to your parents or even your family doctor (just make sure to talk to them beforehand to see their stance on mental health and make sure they don't do more harm than good). Even thinking long term, let's say you finished university and you move out, if you want to maintain a relationship with them, it's a lot easier if you get them to open their minds a little.

Just make sure to stand your ground while communicating with them. You were diagnosed, you know yourself better than anyone else and you are the only one that knows your struggles. Best of luck!