As a user GTK typically feels a little funky on Windows, although I don't know how much of that is a fault with the toolkit and how much of it is a function of Windows definitely not being those developers' primary target.

I'm delighted to hear Rust programmers have got something worth using.

And which GTK library does it need? GTK 1, 2 ,3, 4 or 5 ?

I'll respond to the lame joke. 1 and 2 are dead, 5 doesn't exist, and it supports 3 or 4.