I’m an adult with combined type ADHD.
I feel very strongly that any device which has other apps is a terrible tool for ADHD management and organization. No matter how well intentioned, and I know that you are.
One needs to spend less time on devices. Go analogue. Pen and paper.
The best tool that I have found is the Bullet Journal Method. It takes time, effort, and there is a learning curve. The ROI is higher than from any app. No other tool has impacted my life and productivity more.
That said, I have found some tertiary apps to be helpful, though my BuJo is my compass. Endel for time boxing/Pomodoro, and sleep.
Headspace for guided meditation.
No, it doesn’t have to be aesthetic, with pretty lettering and doodles (as seen in social media).