Define "large" :

https://www.astralcodexten.com/p/fall-meetups-everywhere-cal...

(One of the largest subgroups AFAIK ?)

(They still seem to be leaning heavily USA-based, and in particular California-based.)

Maybe a better link would be to the previous wave of meetups, because some places join the event at the last moment:

https://www.astralcodexten.com/p/meetups-everywhere-spring-2...