When you a new to XMPP and just installed your client and connected to some XMPP server, you will notice: there is no contact for you to chat with!
This is contrary to Facebook, WhatsApp or Signal where you upload your personal address book with all of your known contacts to a central server. And if you ask me, this is a good thing that XMPP is not doing that stuff. There are some websites where users voluntarily publish their Jabber IDs. And there is Quicksy, an XMPP service/client that uses phone numbers as Jabber IDs where you also can publish your own Jabber ID.
So, when there is no central directory, how can you find contacts? Well, the answer is simple: with XMPP you can not only have 1:1 chats with other people, but also join chat rooms, so called “Multi User Chats”, or in short: MUCs. And for MUCs there is a search engine and a directory for that on: https://search.jabber.network
For a start how about joining the MUC for the client you are using or some MUCs based on your interests:
- Dino-im: xmpp:firstname.lastname@example.org
- Conversations: xmpp:email@example.com
- BeagleIM/SiskinIM/StorchIM: xmpp:firstname.lastname@example.org
- Gajim: xmpp:email@example.com
- Movim: xmpp:firstname.lastname@example.org
- Debian: xmpp:email@example.com
- or for all XMPP server operators: xmpp:firstname.lastname@example.org
You got the point, I guess.
And did you know that some mail providers such as mailbox.org also provide XMPP access? So, when you have contacts with such addresses, you can contact them not only by mail but also by direct messaging them via your XMPP clients and add them as your XMPP contacts as well.
That way you can easily grow your network of XMPP contacts without the need of a central directory server or uploading your personal addressbook to some servers.
Oh! And when you say that you have already tried XMPP a few years ago: give it another try! There are many huge improvements being made in the last years!