I personally disagree with a lot of the changes GTK4 introduces, but I still think it's my favorite way to build quick little native apps on Linux. If you're well-versed in Rust, I really recommend checking out gtk-rs[0], a fantastic little crate with a surprisingly robust GTK implementation. If you're familiar with 'builder' style tools (particularly Glade), your workflow will feel right at home. Plus, memory safety/type safety/good concurrency and all those other awesome Rust freebies you get are super nice for GUI apps.
[0] https://gtk-rs.org/