A couple of years ago I researched this question for ActivityPub and came up with about 10. I can dig it up if someone wants to try the same methodology here. Mainly looked at GitHub contributor activity in last 6 mos among the major projects. Only took a couple hours.

There is nostr:npub180cvv07tjdrrgpa0j7j7tmnyl2yr6yr7l8j4s3evf6u64th6gkwsyjh6w6 nostr:npub1xtscya34g58tk0z605fvr788k263gsu6cy9x0mhnm87echrgufzsevkk5s, that guy with wit ai generated cat pfp, all the active relay software maintainers (2-3 more I think), all the people behind the different clients (5-6 are the main ones). That takes us to ~12

10, 12, 23, 50 … these numbers are all bias toward “popular” (and prolly grant funded) projects.

I’d guess in the hundreds easily … developers (ppl who touch code) working on all sorts of projects that interact with Nostr relays or clients.

Not including all of the other stakeholders working on or invested in each project.