Yeah, my gut is that of those 30K people on Facebook you might get a few hundred to join a new platform. But maybe not. It probably won't be very useful without the other 29K people plus (even if a lot of those are probably not very active).

Heck, we see this with Mastodon and Bluesky, their content is very thin in my experience (even if Twitter's is also thinner than it used to be at least with the mostly tech-related content I followed).