Both. Trillian was not Mac only (I made a mistake from memory), Pidgin was multi platform but started on Linux. Pidgin had every protocol. I still keep my .purple config folder and logs after over a decade. Not like I’ll ever read the logs again, though.
Edit: Guys, relax. I made a mistake recounting from memory. I didn’t run Windows back then. I assumed that because of the native Aqua interface, there wasn’t a Windows port.
Literary or literally? (hint: neither are correct.)