QTBUG-109609 is related and the example from there can be used to reproduce (that was more about in general putting stuff there, this is about Button not working out of the box).

The text of a button does not show up in accessibility data and therefore tools making use of this data to locate buttons only find buttons without any text.

In native Android application the text field is filled with text of the button.

To reproduce, please run the attached example and observed the "Text" attribute of any of the Buttons for example with Appium tool and it is empty.