Everyone's a nerd about something. What are you a nerd about?
I know it's an unpopular opinion given current circumstances, but I've always been a huge nerd about Russia. The history, the geography, the music, etc. And as an American, I've always found it fascinating how U.S.-Russian relations have fluctuated over time. We've gone from allies, to enemies, to frenemies. This doesn't mean I support Z or Putin, of course. What are you a nerd about?
Is it not intellectual to like something a lot and dive head first into it and learn as much as possible about it? Wanting to learn about something starts off with a spark of passion
also : a person preoccupied with or devoted to a particular activity or field of interest
So a "something" nerd, e.g. a theatre nerd, Star Wars nerd, or what have you, is distinct from using "nerd" on its own. Both definitions are equally valid and widely-understood.
Linguistic prescriptivism is lame #DescriptivistGang😎