Facebook is where real life is at. Nobody uses twitter (now X) to organize things, Instagram is just for advertising already established companies and for brands.
Facebook, meetup and Eventbrite are the places where the very first steps of every local community are taken, but Facebook is superior of course because you can bounce back between building a community and talking to your friends and family, plus you can directly reach members of communities which kinda do the same thing as what you have in mind.
Facebook is essentially the 'do stuff' social media, whereas Instagram is the 'promote stuff' social media and Twitter is the 'dunk on other people and start flame wars' social media.
Unironically if the goal of your online presence is to wind up doing stuff in the real world, then Facebook is the only game in town.