There is a large list of public XMPP servers one can register on ( https://list.jabber.at/ https://list.jabber.at/ & https://xmpp.net/directory.php https://xmpp

There is a large list of public XMPP servers one can register on ( https://list.jabber.at/ https://list.jabber.at/ & https://xmpp.net/directory.php https://xmpp.net/directory.php ) https://movim.eu/ https://movim.eu/ is another option (has a fancy web client, android & linux client and of course supports any XMPP client)