I usually just tell people "I fix shit" or "I build things". Computers and bicycles have been somewhat constant throughout my life though.

Don't get into salt water fish tanks... pistol shrimp are cool as shit... but getting the tank right is not for the ADHD person :)

Comic books even just keeping up with current Arcs... get pretty expensive and then you just have a backlog of 30+ books to read

Beer making is fun... Cleaning up sucks

Gardening wasn't for me... I would get home from work everyday and have to spend an hour or two taming my tomato plants (Like vegetables... hate gardening)

I am sure I have more hobbies abandoned than this. Thats the fun of ADHD. I have abandoned more projects than most people have started