Breathings of polytonic Greek keyboard not working on ALL QT apps

GR-gr keyboard layout doesn't work on all QT apps (Calligra, Kate, Kwrite etc.), but works flawlessy on other not-QT apps like Geany, Libreoffice, Firefox, Google Chrome (where I'm writing), etc.

In short, I can write these chars: ά ὰ ᾶ ᾷ

But in QT apps these chars are not displayed: ἀ ἁ ἄ ἅ ἂ ἃ ἆ etc.

From my tests, in conclusion, the so called smooth and rough breathings and their combinations with other diacritics are NOT displayed.

I made my tests on X system (not Wayland).
Cf. https://bugs.kde.org/show_bug.cgi?id=380047
Thank you very much in advance,
Domenico