All the casinos have their own community, they use tools like Telegram or Discord to let the community interact with theirself. And they us other social networks like X to bring more users to the community.

Normally all the sites have the social network link in the footer, so, that's a good start for you, just open any casino and scroll down to the footer.

And remember, while bigger the casino bigger the community, so, don't expect big communities on new or untrusted sites.