Throw out what you've been told about sitting cross-legged for twenty minutes and trying for a "blank mind." That sentence alone was written by someone whose brain has only barely a few tabs running at once, can you meditate with music.
The ADHD brain thrives on dopamine and novelty, and a stream of sensory information, so the opposite of those things (quiet, silence, repetition) when asked of us, would in most people cause them to feel not good enough, like everyone else would; but also feel like a massive letdown. Which, again, does not ever come from willpower, it comes from a mismatched approach. Start with two minutes.
Do not try for ten.
Genuinely aim for two minutes instead; which, in the first 30 seconds of which, you are going to lose it in some kind of spectacular way anyway; so with all due respect, the less runway you have when it first zooms away, the less time it has to get away from you —and you can bring it back! Success is simply circling back —and this is your entire rep. Doing the rep for 50 occasions throughout two minutes —you would most certainly generate a stronger attention muscle than someone who just remained still for twenty minutes on the floor —totally aware of absolutely nothing.
Physical motion helps a lot; a walking practice, free-form dancing, even wandering the house; or anything physical at all while working on mindfulness... Anything! Try pacing the house or the room with something tactile and just tune into your breath when it isn't a good situation at all,if anyone in the world were to watch your behavior! Believe it or not... "do the dishes" meditation (water running, hands in motion and mind in its body) is more often than not how the most present, intelligent minds truly find peace with meditation instead of a perfectly poised, straight-out-of-a-yoga-magazine, meditative bliss pose.
Noise can be another rescue where total stillness becomes hard to sit with in an ADHD brain. Listen to your favorite meditation recordings, binaural beats, or even just the tick of a clock in your room and your brain will do the rest by latching onto whatever thing it is listening to!
Timing of this meditation session during your day matters too... Should you have prescription medication that you take during the day then this is typically a much better time than right when you wake up, when your brain is far from switched on.