Hi Plum, finding a hobby whilst having ADHD can be difficult, and there's no harm in going through a few different hobbies at a time. Here are some suggestions of things that I have personally tried and liked
1) Crochet - I find this to be very relaxing and once you know the basics, you will find that a lot of the patterns are just repeats of the stitches you already know
2) Colouring - people often assume colouring is just for kids, but I'm here to tell you that's not the case. There are plenty of colouring books aimed at adults that you may enjoy
3) Scrapbooking/journalling - it doesn't have to be on anything in particular, fill a whole page with fun stickers if you like, whatever makes you happy
4) Researching - not so sure this is a hobby, but you can research about hobbies. It gives you a great opportunity to hyperfocus if you find the topic interesting. Then you can make documents of your findings and info dump if you like
I hope these suggestions can prove useful to you and you find a hobby soon. Best of luck!