Qt by default uses native widgets wherever possible
Not true. Qt widgets appear to be native, but in fact they are not (but your post is proof that they made quite a good job with the appearance). This is a bit of problem on macos where Qt has some issues with appearance (or at least used to have).
And over there, I'm demonlapin (925).
Nothing will ever be attempted if all possible objections must be first overcome. -- Dr. Johnson