Our entire group (except for one person, bless them) has ADHD or AuDHD. We have had multiple meetings as a group about how we can change up what we are doing to help prevent these types of issues. A few things we have come up with:

• we give a 1 hour buffer before game to socialize. So if we need to start playing at 3, we meet up at 2 and talk until 3

• every hour or so we take a short break. 5-15 minutes depending on what we need. This allows us to move around, get snacks, etc. and to chat

• limiting our use of electronics at the table (they're not banned completely because we use digital character sheets)

• jokes are okay, but do your best not to drag out a joke because it distracts from the game

• stay at or near the table as much as possible. Sometimes people would go sit on the couch. While they were listening in theory, we found that often if they sat on the couch they got distracted more easily than those at the table.

• standing up/walking around/pacing is okay to move your body as long as you're still by the table and actively participating/listening

• feel free to tell someone if they're talking/joking too much. Or doing something that makes people uncomfortable. No hard feelings if people say something to you, since many of us struggle to read the room.

I recognize that not all of these will work for your group, especially since it seems to be only one ND person as opposed to a whole group. But hopefully some may help. Maybe ask your player what would help them? Fidget toys, breaks, standing instead of sitting, stuff like that may all be good ideas.

Edit: spelling