I was always more of an MSN Messenger guy. But the Open OSCAR Server project is a fantastic labor of love stewarded by a kind soul.
They put up with (if not were outright amused at) me digging up the weirdest 3rd party clients I could [1] and just kicking them around against the server software to find bugs [2]
[1] https://wiki.cursedsilicon.net/wiki/AIM_Clients
[2] https://github.com/mk6i/open-oscar-server/issues/120