Repeat a mantra in your head. The mantra could be anything really. You do not need imagery to meditate. Another trick is to look at your hand and try to feel/sense the inside of your hand, focus on that.

I am on the other end of the phantasia spectrum; I have hyperphantasia. This causes problems with meditation because my ADHD gives me intrusive imagery.

The key with meditation is to just keep trying. Mediation is an incredibly useful tool but it is something you have to constantly practice. It is harder for people with ADHD to accomplish consistently but it is entirely possible to learn to do it well. If you practice enough you may learn how to live most of your life while meditating.

Learning how to meditate was the turning point to gaining control of my life and start on the road to a functional life. I am not saying medication (I’m on Vyvanse) and therapy (once a week for me) aren’t equally important or weren’t major contributors to better understanding and living with my condition but learning how to meditate and doing it consistently was when things started to click for me.