Following up on this... I was Miranda user. With it I was able to run ICQ, MSN Messenger and other instant messengers with an encrypted layer slapped on top (as long as I was able to talk my friends out of using the official client). Today it's called Miranda NG[1] and it seems alive and kicking[2].

[1] https://www.miranda-ng.org/en/ [2] https://github.com/miranda-ng/miranda-ng