You probably mean general purpose libraries, when it comes to libraries that need to interact with OS native APIs Tauri does the heavy lifting by implementing for all platforms including Android and iOS.

I mean every language is cross-platform at its core, even Node, but for more complex calls things get really tricky.

Can it be used to develop for Linux?

Plugin are a feature when it provides cross platform abstraction for Windows, Linux, Mac, Android and iOS.

Doing it natively means I need to make a few thousands of extra ifs and maintain all different ifs for each platform, while Tauri provides it out of the box. Such as notifications, filesystem access, file opener, auto start, window management and etc...