I should add that I have a group of friends that only chat on "C", for C in:

* SMS * Apple iMessage * Email * IRC * Facebook Messenger * Telegram * Slack * Webex Teams * Discord * Twitter (DMs) * Signal * Whatsapp * A particular PHPBB web forum

Instead of being on top of all of these, I mostly neglect all of them, and then friends complain that they haven't been able to get a hold of me for 6 months.

XMPP was my own "solution" to this problem, which nobody else used.