> cross-platform GUIs always look bad outside of the "main" platform

qBittorrent looks great on KDE, and would look great on macOS too if they used native icons (I’ve made a theme for that but was too lazy to install it when I was switching laptops). No idea about Gnome and Windows, but probably alright as well.

So, Qt can get you a long way. But you should of course adapt your app to platform conventions and guidelines.