I've only tried mindfulness meditation, but as others have chimed in in the thread, other types may be easier depending on your circumstance. As I started, even being able to focus for 5-10s uninterrupted by thought was a huge win. It may be slow, but eventually you will be able to extend these periods and get to a point where it's actually 'working'.

Also, I don't think using stimulants or other adhd meds (like atomoxetine), if they're part of your routine is necessarily cheating. I like to think of them as 'training wheels', which will help you focus internally and less on your thoughts. It will still be difficult (like it is even for those who don't have ADHD), but it may help your brain start shaping those neural important pathways a bit sooner and more easily than it'd otherwise come unmedicated.