XMPP has explicit support for "transports"/"gateways" for that purpose, so you could plug in AIM/ICQ/whatev support into your XMPP server. See https://spectrum.

XMPP has explicit support for "transports"/"gateways" for that purpose, so you could plug in AIM/ICQ/whatev support into your XMPP server. See https://spectrum.im/documentation/about.html https://spectrum.im/documentation/about.html for example. IRC has bitlbee (and probably others) to fulfill that role https://www.bitlbee.org/main.php/news.r.html https://www.bitlbee.org/main.php/news.r.html Matrix has "bridges" to interop with other protocols https://matrix.org/bridges/ https://matrix.org/bridges/