Do you mind to prove some example of communities popular? Sorry but I haven't had facebook since 2016 and I literally have no idea what is going on with it.
I don't live in the US. We have groups for uni, the tech sector (in general, kind of like /r/programming in a way), ML&DL, dating, sales (alongside Facebook Marketplace). We also have groups for towns and neighborhoods as the prime way for the locals to communicate. It is de-facto reddit here