Jabber is a federated chat platform not so different from IRC or Matrix. It's based on an open protocol named XMPP, that's secretly used in more places than you'd expect.
My current home on the network is JabberFR (at PulkoMandy's recommendation) and my client of choice right now is Psi Plus. Both have fairly extensive wikis on their respective sites.
These days I also resumed looking into Movim, a social network built on top of XMPP, much like Mastodon and Lemmy are based on ActivityPub. It's not on par with Discord or Tumblr quite yet, but damn if it's not getting really close now. My test blog there is kind of empty for now, but I have to start somewhere.
A personal blog can be created on Movim with any XMPP account, not necessarily from the same server. Turns out, that's because feeds are in fact a feature of the protocol, supported by a few other clients such as Monocles Chat. What Movim can do is give your microblog a public address on the web.
Conversely, ask the admins before making a community. To make just one group chat or three, on some servers you don't need any permission; on others it's frowned upon to make your own willy-nilly. If it doubt, use service discovery on your own server first.
(Contrast with Matrix, where it's self-understood that everyone is welcome to create their own spaces and rooms.)