A cross-platform MSNP client. Still a work in progress, but it has a decent set of features.
MSNP was the protocol used by MSN Messenger, with this client using version 15 of the protocol. Though Messenger has been dead for years now, there are third-party servers such as CrossTalk that implement those MSNP versions and more, thus reviving official clients and working with old and new third-party ones.
This project was made with C# and Avalonia, and is available for Windows, Linux and MacOS here.