I believe Trillian still continued to support other networks (as long as they could) after introducing "Astra" or whatever they called their own chat network. Most of them have died off over time or locked out 3rd party clients (AIM, Google, Yahoo, MSN, etc.).
I haven't used Adium in like 15 years but that honking noise will be with me for eternity.
Trillian used to be like Pidgin and Adium on Windows but then they went and made its own IM service.