In regards to the ADHD part, I found from my own experience that running games that are deliberately built more around table collaboration and improvisation to be a better fit for me, since it made prepping much easier. There's still some preparation work involved, but it was more centered around things I enjoyed preparing (characters the players may run into, potential things that could happen and so on).
In terms of running, there's no shame in asking your table for ideas, if you can't think of something cool. Sure, you're technically "running" the game, but in the end the table as whole creates the story, plus people tend to be more interested in the story, when they feel they have some degree of control over it.
But overall, just finding a space that lets you get used to running games in general, is probably the most helpful thing. In the end, what parts of running a game you enjoy and how you run games, are completely unique to you, but to figure those out, requires a space to experiment and to also make mistakes.
Edit:
More practical ADHD things:
Have dedicated notes for anything that might be important but is something that is easy to forget as well.
For me it's things like player character names and pronouns, a list of potential complications for failed rolls, a list of potential NPCs, another list with additional names, in case I quickly have to invent a new person, and so on.