Pidgin[0][1] supports a great deal of protocols and there is "End-to-end encryption, through Off-the-Record Messaging (OTR)" plugin you can install that can be used for just about everything it supports. If ICQ NEW still supports OSCAR it can probably used out of the box, there is also a plugin[2] for the newer WIM protocol.
Pidgin feels like it's dated by now, doesn't support much, does it even support Matrix (out of the box)? I think it still lists some dead protocols last I looked at it too.
pidgin doesn’t support matrix out of the box; we did write a prpl a few years ago but it needs a maintainer to make it properly fit for purpose: https://github.com/matrix-org/purple-matrix
[0] https://www.pidgin.im/
[1] https://en.wikipedia.org/wiki/Pidgin_(software)
[2] https://github.com/EionRobb/icyque