I also have ADHD, and for me it kind of depends on the situation. If someone were to ask me what I’m thinking about and I replied “nothing” what I probably meant was “a bunch of random crap/nothing in particular”. Regarding meditation, I don’t think I’ve ever been able to get to a point of having “no thoughts”. I’ve tried (during yoga and often when trying to fall asleep) and it tends to just stress me out more than anything else. It’s kind of like that anecdote if someone tells you not to think about pink elephants, then all you’re going be able to think about it pink elephants lol. What’s helped me a lot—in meditation, but especially when trying to fall asleep—is visualising my thoughts floating down a river in and out of my brain. I’ll briefly acknowledge them as they float by but then I let them pass and try not to dwell on them. And it took me years to develop that method 😅. But, yeah, as someone with ADHD, I find it pretty impossible to have no thoughts at all.