Qt is using a default cursor for Qt::PointingHandCursor instead of the cursor from the system theme on Ubuntu (a small black left hointing hand). TO reproduce, run the following, simple example. Interestingly, this only affects that one cursor, all other cursor types such as arrow, resize, etc are correct.

Also when I try to take a screenshot, the cursor in the screenshot is correct, even though the cursor I can see is wrong.

#include <QApplication>
#include <QMainWindow>

int main(int argc, char **argv) {
QApplication app(argc, argv);
QMainWindow *w = new QMainWindow();
w->setCursor(Qt::PointingHandCursor);
w->show();
app.exec()
}