Some of QT is LGPL, other parts are GPL.

The question about dynamic linking is valid, since Rust's build system, Cargo, produces a static binary by default.

Cargo links all the rust code together in a static binary, but the C/C++ libraries can be linked dynamically, and in the case of something like Qt, most certainly are.

Since most important part of Qt are LGPL, you can use this crate and other Qt binding crates to develop proprietary applications.

(Only if you wish to use one of the few parts that are "only" GPL, then you need to release the final product and all its parts under the GPL, or acquire a Qt license)

You can even link rust to rust dynamically, though it's very unsafe and will break if you use different compiler versions