I think ejabberd or another other xmpp server would have been my first choice for a service like this by a long shot. If only we had some good iOS clients to go to. While I’m on android, most of the family and some of the friends use iOS, so it was kind of a non-starter from that alone.
Edit: log -> long
If you’re ok with just file storage sftpgo has been solid for me for years now. Does sftp ftp and WebDAV (like nextcloud). Webui isn’t as pretty but it’s fast. Mobile apps will be various sync apps with sftp or WebDAV support. On Android folder sync pro is pretty good for keeping documents and pictures backed up