Hm, Jvm also gives access to Kotlin and Scala, I'll definitely have to look into it.
Qt development can be excellent or nightmarish, sometimes both. I don't know enough to know why the disparity but I've been adjacent to teams that love qt and ones that loathe it. I'm guessing a big aspect is state management; qt predates the reactive revolution, and IIRC is prone (as is any gui) to callback hell.
Overall Qt is quite nice and works portably across platforms. You're right about callback hell but there's a fox for it. Personally I prefer to create a bunch of overloaded utility functions for different widgets and data types and in each utility function i use QSignalBlocker to make sure I'm not accidentally invoking any callbacks. I condiser any "raw" Qt "setXYZ" call to be a bug.
Just as a fun test a while ago I made a small desktop app with scala and scalafx/javafx. It's not bad, gives you some of the nice things you get from js guis (reactive rather than loads of callbacks etc).
I don't know what the development side is like, but as a user I do find Qt apps to be fairly nice.
I also think Java (Swing) apps are basically fine. Java was "bloated" back in the day, but not relative to what else is in use today.